« Linux | Main | news »

Tuesday, 09 May, 2017

MySQL Performance: 8.0-dev Progress Details

As promised, here is the follow up of the MySQL 8.0-dev Progress teaser ;-)

so, yes, we expect to see the most hot contentions gone, as it's seen from the following graph :

Observations :

  • the graph is representing the spin waits / spin rounds events happening during the same Sysbench Update-NoKEY workload
  • the load is progressing from 8 concurrent users to 16, 32, .. 512
  • 3 engines are tested one after one : MySQL 5.7, MySQL 8.0 (current DMR), MySQL 8.0-dev (current prototype)
  • first all 3 engines are running on 22cores-HT only (1 CPU socket)
  • then, the second time : on 44cores-HT (2 CPU sockets)
  • and the most important thing to retain about this graph is that on 8.0-dev we see all main hot contentions gone ;-)
And not having all these contentions is resulting in the following :

Observations :
  • one of the most painful things about current InnoDB WRITE performance is its scalability.. (in fact the absence of scalability ;-))
  • the problem is not new, just that since READ scalability was greatly improved since MySQL 5.7, seeing WRITE to remain not scaling become even more painful..
  • and this is because of all overhead and contentions we have on REDO level, transactions & lock management, etc..
  • so, MySQL 5.7 and 8.0 DMR are limited by this, and moving from 1 CPU socket to 2 CPU socket cannot help here (in fact the things may become only worse as with more CPU cores all these contentions will become only higher)..
  • while 8.0-dev code is giving us a huge expectation to finally see all these problems gone, and potentially get x2 times better performance even on a single CPU socket !! ;-))
  • NOTE : we're not running for "high numbers" here, there was a long and hard battle to see performance improvement since a low load as well, so a positive difference is already seen on 8 users, and even more seen since 16 ;-)

However, this is not the only benefit.. -- the story is going way more far, because all this deep remastering is potentially allowing us to get a rid of all the overhead we see when READ COMMITTED (RC) transaction isolation is used.. - example of such an overhead you can see from here :
- http://dimitrik.free.fr/blog/archives/2015/02/mysql-performance-impact-of-innodb-transaction-isolation-modes-in-mysql-57.html

and this was one of many reasons why REPEATABLE READ (RR) transaction isolation is historically used within InnoDB by default (and still continue to be the default in MySQL 5.7)..

While potentially with 8.0-dev the things could finally change ;-)

The following graphs are representing the results from Sysbench OLTP_RW workload comparing MySQL 5.7 and 8.0-dev :

Observations :
  • first the test is executed with RR isolation on both 5.7 and 8.0-dev
  • yes, 8.0-dev is doing better than 5.7, but the most important is the next ;-)
  • the next step both are executed with RC isolation
  • and then you can see TPS on 5.7 going lower..
  • while on 8.0-dev TPS level remains just the same on RC as on RR !! ;-)
So, crossing fingers, if all is going as expected, this could allow us for the first time to have RC isolation in InnoDB as default.. -- what does it mean for all MySQL users and their apps ?.. => huge overall experience changes + less headache + less locking conflict, etc. etc. etc. (and to not go very far, just to mention the yesterday's article from Alex : https://www.percona.com/blog/2017/05/08/chasing-a-hung-transaction-in-mysql-innodb-history-length-strikes-back/)..

Well, work in progress, crossing fingers, stay tuned ;-))

the last remark: just to bring your attention once more that MySQL 8.0 is moved to have UTF8 charset by default !!! => so, if you're planning to run any tests with 8.0 DMR, please, mind to remember this !! - so use UTF8 on both sides (server and client) and consider the UTF8 overhead, or switch the server back to latin1 if your "client" apps are latin1.. -- otherwise you'll not be happy ;-))

more benchmark results and further observations about MySQL 8.0-dev you can find in my slides :
- MySQL-8.0-dev-Benchmarks-Scalability-Apr.2017-dim.pdf

Thank you for using MySQL ! and Go MySQL !! ;-))

Posted by Dimitri at 21:05 - Comments...
Categories: MySQL

Friday, 14 April, 2017

MySQL Performance: 8.0-dev Progress..

As you already know, a new MySQL-8.0 milestone release is available (and hope you did not miss all the news coming from MySQL Server Team site - starting by what's new article and followed by many others (and you'll see yet more to come ;-))..

There are also many good changes improving overall MySQL 8.0 Performance. However to see a real boost on OLTP workloads you'll need to have little bit more of patience.. -- we're attacking InnoDB fundamentals.. -- the parts of design which are probably remained mostly unchanged since InnoDB creation ;-)) -- you can easily understand that such a work has a long road from idea/ prototype to a final release.. On the same time our "Preview" results are looking very encouraging, and I'll be happy to say you more about during my talk @PerconaLive, 27/Apr 1:50pm :

- https://www.percona.com/live/17/sessions/mysql-80-performance-scalability-benchmarks

to give you a first idea about what is coming, I'll post here a singe "teaser" graph about a pure UPDATE performance on 22cores-HT (1CPU socket), then 44cores-HT server (2CPU sockets (kind of today's "commodity" HW ;-)) -- the graph is taken from the results comparing MySQL 5.7 vs current 8.0 vs 8.0-dev (which is yet in dev progress), but instead of TPS/QPS you can see here just levels about InnoDB internal contentions :

Your browser is not supporting SVG..

to help you little bit to find the diff within these graphs, in short :

  • yes, log_sys contention is gone in MySQL 8.0-dev ;-)
  • and log_write too..
  • and trx_sys..
  • and lock_sys..
  • and...

If it's saying you something, you could already get a first idea about what kind of TPS boost you may expect and what kind of possibilities it opens.. ;-) -- but if not, don't worry.. -- I'll tell you all this during my talk in 2 weeks ;-)

(yes, slides will be published, no worry; and yes, this article will be also updated with more details)

until then, stay tuned.. ;-))

And THANK YOU for using MySQL !!!

UPDATE: the follow up article is here - http://dimitrik.free.fr/blog/archives/2017/05/mysql-performance-80dev-progress-details.html


Posted by Dimitri at 2:10 - Comments...
Categories: MySQL

Tuesday, 03 May, 2016

My slides about MySQL Performance from #PerconaLive Apr.2016 US

As promised, here are my slides from Percona Live Conference in US, Apr.2016 :

  • MySQL 5.7 Performance & Scalability Benchmarks (PDF)
  • MySQL 5.7 Demystified Tuning (PDF)

Feel free to ask any questions or details you're needing, etc..

Also, not really related to MySQL, but as I was asked so many times about "how did you manage to project your slides from Mac, but drive it an annotate via iPad?" - here is a short HOWTO:
  • you need to have Keynote app installed on both your Mac and iPad
  • you create your own WiFi Network on your Mac (MenuBar->WiFi->Create Network...)
  • once done, connect to this WiFi Network your iPad
  • (having your own network is getting a rid of any potential sync issues, removing any dependency on wifi availability in a room, as well allowing you to walk way far from your Mac and still keep a control on your slides ;-))
  • then you're starting your Keynote presentation projection on your Mac
  • after what opening Keynote app on your iPad
    • "clicking" on Keynote Remote
    • selecting your Mac from the list of available devices
    • and you're getting hands on your currently projected slides ;-))
    • you can select then a preferred layout: current slide, current + next, current + notes, etc.
    • AND on any slide you can involve an annotation and draw over the slide with pencils of different color to point on one or another part of your slides
    • (of course, the drawing you're doing remains only during annotation and not destroying your slides ;-))
  • have fun! ;-))

What else to say? The conference was really great and I may only admit that Percona is doing it better and better from year to year.. Huge amount of very interesting talks, great technical content mostly everywhere, a lot of innovation, new ideas, deep discussions, etc. etc.. -- you don't know what you're missing if you were not there ;-))

Well, time for the rest now, and as a final point - a "Bloody Cheesecake" on my departure from SFO Airport
(for those who understand ;-))

Posted by Dimitri at 16:39 - Comments...
Categories: MySQL

Tuesday, 16 February, 2016

MySQL Performance: PFS and Checksums impact on OLTP_RW Benchmark with MySQL 5.7

This article is the follow-up on discussion started around MySQL 5.7 results on OLTP_RW Benchmark.. -- the point was about the impact of PERFORMANCE_SCHEMA (PFS) enabled, and InnoDB checksums on MySQL 5.7 performance within this OLTP_RW workload.

As promised, here are the results:

Just in case if the legend naming in graphs is not obvious :

  • PS-off : "performance_schema=off" was used
  • PS-def : "performance_schema=on" was used (default PFS instrumentation)
  • chksum0 : "innodb_checksums=0" was used
  • chksum1 : "innodb_checksums=0, innodb_checksum_algorithm=crc32" was used

OLTP_RW 1M x8-tables MySQL 5.7 (config: trx_commit=2 double_write=0) :

OLTP_RW 1M x8-tables MySQL 5.7 (config: trx_commit=1 double_write=0) :

OLTP_RW 1M x8-tables MySQL 5.7 (config: trx_commit=1 double_write=1) :

  • the impact of checksums is near zero when OLTP_RW workload is running on MySQL 5.7 with a less safe config (trx_commit=2)
  • the checksum impact is bigger on trx_commit=1 (but not growing more since double_write is also enabled)
  • something similar goes with PFS impact as well..
  • however this gives me an expectation that once we'll fix the slowdown issues due trx_commit=1, we'll lower as well PFS impact here too (like it was already happened in the past)..
  • so far, the checksum impact here is around 0-2%, while PFS impact is around 3%-7% (mostly bigger on higher concurrency load)
  • interesting that "combined" impact of both (checksums + PFS=on) is not really much different from just PFS=on
  • NOTE : if you're really worry a lot about CPU cycles used by PFS instrumentation -- since MySQL 5.7 you can compile MySQL binary yourself with various PFS compile flags to completely disable some kind of instrumentations you're sure you'll never use (for ex. mutexes/rw-locks, etc.) -- I'm not doing so, but you can ;-))
  • NOTE : from the past experience I've also observed that compiling MySQL binaries without "-fno-omit-frame-pointer" option may give you additional 5%-10% speed-up !! (however, you'll not be able anymore to get a proper stack trace from a running process or in case of crash..) -- I'm not doing so, but you can ;-))
  • but well, what is important here is that with or without PFS/checksums enabled MySQL 5.7 is still reaching over 40K TPS performance level on this workload, and it's still way bigger than I've ever observed on MySQL until now ;-))
  • and our challenge here is to bring trx_commit=1 to the same level as trx_commit=2, and largely reduce the impact of double_write.. (but this is another story, stay tuned ;-))

As usual, any comments are welcome! And Thank You for using MySQL! ;-))


Posted by Dimitri at 19:22 - Comments...
Categories: MySQL

Tuesday, 09 February, 2016

MySQL Performance: Scalability on OLTP_RW Benchmark with MySQL 5.7

Next article from the MySQL 5.7 Performance stories, now about OLTP_RW scalability (if you missed any previous ones, see 1.6M SQL Query/sec (QPS) with MySQL 5.7, 1M SQL Query/sec on mixed OLTP_RO / true Point-Selects performance / over 100K Connect/sec Rate / Re:Visiting nnoDB vs MyISAM Performance -- all with MySQL 5.7)..

Before we'll start looking on OLTP_RW results, let me explain first why we payed so many attention to MySQL 5.7 Performance in RO (read-only) workloads (and all my previous posts were mostly about RO as well).. -- the reason is very simple: there is no great RW performance if RO is lagging.. And also because we were pretty bad on RO before 5.7 ;-))

Let's get a look on the following graphs :

  • the graphs are representing the test results obtained more than 2 years ago..
  • they are all obtained from the same 32cores-HT server (4CPU sockets, each with 8cores-HT)
  • and we were looking for the best possible MySQL server performance on this host by limiting MySQL instance to be running on 1/2/4CPUs (8/16/32cores) and using/not-using CPU HyperThreading (HT) (16cores-HT vs 16cores, etc.)..

So, what we observed over 2 years when MySQL 5.7 development was just started ?..

Here are the results obtained on OLTP_RO workload on MySQL 5.5 / 5.6 / and 5.7 on that time :

Observations :
  • on MySQL 5.5 :
    • the results on 16cores-HT are x2 times better than on 32cores..
  • on MySQL 5.6 :
    • the results on 32cores are just slightly better than on 16cores-HT
    • as well the difference between 32cores vs 32cores-HT results is pretty small..
  • on MySQL 5.7 :
    • same as on 5.6, the results on 32cores are just slightly better than on 16cores-HT
    • but near no difference at all in 32cores vs 32cores-HT results..
    • and, the most painful, is that an overall result is worse than on MySQL 5.6 (!)..
  • this was the first painful point from where MySQL 5.7 was started over 2 years ago ;-))
  • (and probably you're better understanding now why we're so happy to see MySQL 5.7 scaling really well today and easily reaching now over 1M QPS on the same OLTP_RO workload ;-))

But well, let's go back 2 years ago again, and see also what it was about OLTP_RW workload on that time :

The following are the similar test results on MySQL 5.5/ 5.6/ 5.7 , but about OLTP_RW :

Observations :
  • I think you may observe the same tendency by yourself :
    • MySQL 5.5 is scaling up to only 16cores-HT
    • on MySQL 5.6 and 5.7 the results on 32cores are better than on 16cores
    • the benefit from CPU HyperThreading is better seen on 32cores-HT now (but not that big as on 16cores-HT)
    • however, MySQL 5.7 is better "resisting" to a higher concurrent users load
    • while the Max peak TPS is still reached by MySQL 5.6, and not 5.7 ;-))
  • but the most killing here is not this..
  • in fact the presented OLTP_RW results are intentionally presented in QPS (Query/sec) and not in TPS (Transactions/sec)
  • this is making OLTP_RW results "comparable" with OLTP_RO ;-))
  • from where you may discover the painful point #2 :
    • over 2 years ago our OLTP_RW performance was better than OLTP_RO (!!!)
    • and this was true for all presented MySQL versions on that time..
    • NOTE : OLTP_RW workload is including OLTP_RO ;-))
    • NOTE (again) : to be exact, OLTP_RW is extending OLTP_RO by adding write operations (INSERT, DELETE, UPDATE), so we're writing to the disk, we're logging every transaction, we're hitting transaction/REDO locking, and we're still reaching a higher QPS level than a pure OLTP_RO running fully in-memory... -- and this is all because our transactions management in InnoDB on that time was very heavy on locks and did not scale at all..
  • Hope you can better understand now our frustration level 2 years ago, and challenges we faced on that time ;-))

That's why so many efforts were spent to improve InnoDB performance in MySQL 5.7 on RO workloads.. -- was this challenge fully completed?.. -- not yet (some specific cases (block lock, AHI, etc.) are still remaining; then many new functionality features were added in MySQL 5.7 over a time, and adding more code making an overall code path more long as well, so on low load RO workloads you may observe some slight regressions with MySQL 5.7 today.. -- however, as soon as your load is growing, you'll see a real benefit from improved MySQL 5.7 scalability ;-)) Le's say that with MySQL we got a rid of the "main scalability show-stopper" for RO workloads! - and, of course, we don't stop here, work in progress, and yet more other improvements are in our TODO list ;-))

Now, what about MySQL 5.7 Performance on RW workloads ?..
  • the main InnoDB RW scalability show-stopper (generally and particularly in MySQL 5.7) is REDO log locking (log_sys mutex)
  • well, to be exact, log_sys contention is the "final" show-stopper ;-))
  • while before hitting log_sys, you may hit and be blocked by :
    • index lock contention (big stopper for RW workloads, was finally fixed since MySQL 5.7 only.. -- before the only possible "workaround" was to use partitioning (this will split your hot table in several tables (partitions), means split your index as well, means split your contention by the number of partitions, etc)..
    • transaction lock (trx_sys mutex) -- greatly improved in MySQL 5.7 too
    • lock_sys overhead -- lowered in MySQL 5.7, but need yet to be more improved..
    • AHI (Adaptive Hash Index) contention (btr_search_latch RW-lock) -- there is a huge story behind it, but to make it short - you're better to disable it on RW workloads, as every data modification is involving AHI update (e.g. write lock), and you're quickly hitting a serialization here.. (work in progress to improve it)..
  • but well, as soon as you're using MySQL 5.7, your main RW "scalability limit" will be mostly log_sys contention ;-))
  • and, unfortunately, we were not able on MySQL 5.7 timeframe to improve this part of code as much as we made it for RO issues..
  • a true fix is requiring a complete REDO log management re-design, and our timing was not favorable here..
  • however, a probe prototype of the potential new solution showed us a great improvement (you can see its impact in the past LinkBench test results on MySQL 5.7)..
  • the amazing part of this probe patch was that we were able to reach the same or better performance while using innodb_flush_log_at_trx_commit=1 (and flushing REDO log on every transaction) vs innodb_flush_log_at_trx_commit=2 (flushing REDO log only once per second).. -- this clearly proved that the main issue here is not the IO related fsync() of REDO log file, but the REDO log management itself..
  • but well, we're not yet there ;-))
  • so, while our MySQL 5.7 scalability on RW workloads got more better with innodb_flush_log_at_trx_commit=2, we're not really better with innodb_flush_log_at_trx_commit=1 yet (and on low loads / small HW configs you may see no difference vs MySQL 5.6) -- in fact getting other contentions lowered, the log_sys contention became more hot, and there is nothing to do with it, except to get it fixed, so the work in progress is here too ;-)) -- while with MySQL 5.6 you may still hit instead many other problems which were fixed only since MySQL 5.7, so the best answer here will be only your own test validation..

Well, this was about internal contentions which may limit RW scalability. While there are still few more factors :
  • trx_commit (trx) -- already mentioning before (innodb_flush_log_at_trx_commit=0/2/1) and, of course, flushing REDO log data to disk on every transaction commit (innodb_flush_log_at_trx_commit=1) for sure will bring more penalty if you're flushing REDO only once per second (innodb_flush_log_at_trx_commit=2) -- while the risk here is to loose the last second transaction(s) only (and maybe even nothing if your OS & storage did not crash or if you're using semi-sync replication, or even less than last 1 sec (because in reality REDO log with innodb_flush_log_at_trx_commit=2 is still flushed more often than once per second), and even many "serious companies" are doing so, etc.etc.) -- but well, you're always better to evaluate what is valid for your own production ;-))

  • flush_method -- as you're writing to disk, you have to choose the way how your page writes will be flushed to the disk.. -- InnoDB has several options here (and you may find many discussions around and different people defending different option preferences, etc.) -- I'd say from all the past experience and fighting various issues with FS cache, my preferred option here will be to use O_DIRECT (or O_DIRECT_NOFSYNC when available) combined with AIO (innodb_flush_method=O_DIRECT_NOFSYNC and innodb_use_native_aio=1). And, curiously, I'm still prefer EXT4 (while many are claiming XFS is better) -- will post my observations later about ;-))

  • double_write (dblwr) -- the only solution InnoDB has to protect your data from partially written pages on system crash (so, InnoDB will write each page twice: first on dblwr buffer disk space (sys tablespace), and once the write is confirmed, the page is written on its own place (and if on that write the system will crash, the valid page copy will be recovered from dblwr)) -- while I often hear that on the "modern HW" not need to care about, the risk is still here ;-)) and it's still up to you to decide will you turn this protection ON or OFF (innodb_doublewrite=1/0). However, there are several alternatives are possible:
    • you may buy Fusion-io flash card and use their NVMFS filesystem which is supporting "atomic IO writes" (so each page write is confirmed to be fully written) -- MySQL 5.7 is supporting this card automatically (combined with O_DIRECT)
    • you may use "secured" by-design FS (like ZFS for ex. or ZFS Appliance) -- such a storage solution by definition will garantee you'll never loose any bit of your data ;-)) (on the same time don't be surprised your writes are going slower -- each write (and read!) is hardly verified) -- while this may still be faster than the current dblwr..
    • or use FS with data journal (like EXT4, but you have to use O_DSYNC with it, so some FS cache related surprises are potentially possible ;-))
    • etc..
    • I'd say the HW-based "atomic IO writes" solution is looking as the most strong.. -- but we're working here as well to bring yet more possible options, so stay tuned ;-))

  • purge -- a kind of "garbage collector" in InnoDB, running in background, can be configured with several "purge threads", however you may still see it lagging in your RW workload (can be observed as a growing or remaining high "History List" via "show engine innodb status" or via InnoDB METRICS table) -- the problem with constantly lagging purge is that your data space can be finally completely filled up with a "trash", and your whole database processing will be stopped due no more free disk space available.. The good news with MySQL 5.7 that if even purge is lagging during a high load, it'll be still able to catch up once the load become low and "auto-magically" free the disk space used by UNDO images (this is available only since MySQL 5.7, and in all previous versions the only solution to get all this disk space back was to drop the whole InnoDB instance and restore it from a backup or import from a dump).. -- so, it's important to configure several purge threads to make such a space recovery faster (innodb_purge_threads=4)

  • adaptive flushing -- I'll not go too much in details here as the topic is extremely interesting and worth a dedicated article about, so here will just mention that since MySQL 5.7 you can have several "flushing threads" (cleaners) working in parallel -- the initial analyze about what is going odd was made yet more than 3 years ago with MySQL 5.6 (see: http://dimitrik.free.fr/blog/archives/2012/10/mysql-performance-innodb-buffer-pool-instances-in-56.html for details) -- however this was only the first step in this adventure, and a more advanced design was required ;-)) -- well, we're not yet "perfect" here, yet more to come, will just mention here that using 4 threads is usually ok (innodb_page_cleaners=4), then the IO capacity setting should be adapted to your workload and your storage (ex. innodb_io_capacity=2000 innodb_io_capacity_max=10000), and there is no more danger to use bigger REDO log files (recovery processing is going much more faster now than before, as well only a "really needed" REDO space is used, as well a previously existing "read-on-write" issue on REDO logs was fixed since MySQL 5.7, so using 8GB REDO, or bigger is no more a problem (innodb_log_file_size=1024M innodb_log_files_in_group=8) -- well, sorry to skip the details here, will provide them all later..

  • checksums -- as soon as you're using crc32 option, you're fine ;-)) however, keep in mind that this is not impacting your scalability limits, this is a pure "overhead" (your performance levels will still scale with the same tendency, just that the response times will be higher)..

  • there are some other points/tuning/etc. are coming in the game as well, but let's keep the list short just with the most important ones ;-))

After all this "preface", let's focus now on the OLTP_RW benchmark testing (hope it was not too much boring until now ;-))

So far, my main goal on the following testing is to mainly analyze the scalability of MySQL 5.7 on OLTP_RW workload :
  • means, I don't need a too big database (I'm not testing the storage here ;-))
  • so, the dataset should be :
    • not too small to run fully on CPU caches level ;-))
    • and not too big either to not involve IO reads (otherwise, again, we're testing the storage performance ;-))

My HW platform :
  • for my tests I'll use the 72cores-HT server running OracleLinux-7.2 and having flash storage
  • why 72cores ?..
  • in fact this is a 4CPU sockets server (18cores-HT per CPU socket)
  • so, I can easily test scalability on 1CPU (18cores-HT), 2CPU (36cores-HT) and 4CPU (72cores-HT) by binding my MySQL server to run exclusively on these CPU cores..
  • then, these CPUs are the latest CPU chips from Intel, they are really way more powerful comparing to what I have on my older machines..
  • and this is where the whole HW tendency is going -- you'll see these CPUs on all "big" and "commodity" HW, and even 18cores-HT per CPU is not a limit either, so there are really fun times are coming (and if you're still thinking that "commodity" HW is a host with 4cores -- it's a good time to wake up ;-))

While my main interest here is about MySQL 5.7, I'm also curious to see what are the limits on the other MySQL Engines as well, and I have the following on my list :

MySQL Engines :
  • MySQL 5.7
  • MySQL 5.6
  • MySQL 5.5
  • Percona Server 5.6
  • MariaDB 10.1

Test Scenario :
  • from the previous OLTP_RO test I've already observed that all engines are worse vs MySQL 5.7 when a single table only is used in OLTP test.. -- so, no need to waste a time again to point to the same problem..
  • let's focus then on x8-tables OLTP_RW Sysbench test workload, each table of 1M
  • before each test the database is completely restored from its backup (clean dataset for each test)
  • the load is progressively growing from 8, 16, 32, .. up to 1024 concurrent users
  • each load level is kept at least for 5min (was enough to get an understanding about scalability limits, while I'd prefer more longer steps, while in the current case there was no way to run more longer iterations, as to cover all planned test conditions the whole testing already took over 2 weeks non-stop running ;-))
  • each MySQL Engine is tested within the following configurations :
    • trx2 -- innodb_flush_log_at_trx_commit=2 && innodb_doublewrite=0 (default)
    • trx1 -- innodb_flush_log_at_trx_commit=1 && innodb_doublewrite=0
    • trx1-dblwr1 -- innodb_flush_log_at_trx_commit=1 && innodb_doublewrite=1
  • each configuration is also tested with the following tuning combinations :
    • ccr0-sd6 -- innodb_thread_concurrency=0 (default) && innodb_spin_wait_delay=6 (default)
    • ccr64-sd6 -- innodb_thread_concurrency=64 && innodb_spin_wait_delay=6
    • ccr0-sd6 -- innodb_thread_concurrency=0 && innodb_spin_wait_delay=96
    • ccr64-sd6 -- innodb_thread_concurrency=64 && innodb_spin_wait_delay=96
  • and, finally, all configurations + all tuning combinations are tested on 1, then 2, then 4 CPU sockets (18cores-HT, 36cores-HT, 72cores-HT)..
  • the best obtained results for each Engine from any tested combinations then used to compare performance in different configurations (best-to-best comparison)..

I think I need to explain here a little bit more in details the impact of the mentioned tuning options :
  • thread_concurrency : a well known InnoDB tuning to limit the amount of concurrently running threads (usually no more required since MySQL 5.7 for RO workloads, but still helping for RW -- as we're writing and for sure will involve IO operations + manage various raw/data locking (via mutexes/RW-locks, etc.) -- there is still a significant benefit possible with an "optimal" thread concurrency limitation. Which setting could you consider optimal?.. -- I'd say you need to analyze which peak performance level you're reaching on your workload without concurrency limit (innodb_thread_concurrency=0) and see how many concurrent user sessions are running during this period -- this will be then your main concurrency target (by not allowing more than N concurrent threads you'll be able to keep your performance stable even with a higher load (well, at least not to see it quickly going down ;-)) -- in my cases the most optimal setting was 64 until now (innodb_thread_concurrency=64), while in your case it may be something different as well (this tuning is fully dynamic, so you may do live experiments on any running workload at any time you want ;-))

  • spin_delay : and this tuning is directly related to how internal lock primitives (mutexes/RW-locks) are "spinning" on a lock wait (threads waiting on a lock will "sleep" a given delay between spins before to re-try to acquire a lock again) -- the important point here is that a waiting thread in InnoDB will not really "sleep" on delay, but rather execute a "pause" instruction to CPU, so the CPU will switch to execute another thread(s), and waiting thread will come back as soon as its "pause" is finished (for this reason "show mutex" output about mutex/RW-locks spins/waits is better reflecting as for today InnoDB internal waits stats (as the time spent on a wait is not really wasted)). The question is then which value will be the most optimal here?.. -- again, you can get it only by testing by yourself ;-)) (this tuning is also dynamic) -- the 6 is default value, and I'm usually using 96 (innodb_spin_wait_delay=96) for big enough systems. Again, for RO workloads since MySQL 5.7 it's no more required, while for RW workloads we'll hit log_sys mutex contention for sure, and such a tuning usually may help.. The only problem here is that this setting is applied to all lock primitives together, so you really need to do experiments yourself to see what is better for you. However, by getting rid of hot contentions with every new improvement in InnoDB, we're progressively making the need of such a tuning obsolete.. (work in progress, stay tuned ;-))

Now, let me show the impact of this tuning by example :
  • the following graph is representing MySQL 5.7 results on OLTP_RW test
  • there are 4 results for the same MySQL 5.7, just with different concurrency/spin_delay tuning settings: ccr=0 / 64, sd=6 / 96

Observations :
  • as you can see, tuning the spin_delay for this Engine in this workload giving the most important impact..
  • with spin_delay=6 (sd6) we're getting a better performance up to 64 concurrent users
  • however with spin_delay=96 (sd96) we're going more far up to 128 users, and then able to keep near the same level of performance on a higher load as well..
  • interesting that in this case tuning thread concurrency helps only for sd6 setting, and has no impact on sd96
  • (but by the past experience I know it helps a lot on IO-bound workloads, so no reason to not test it ;-))

The same tuning was applied to all other Engines, and then the best obtained results collected (Max(QPS) or Max(TPS)) for each test case.

Now, if you're curious, let me show you yet few more details about :
  • so, the next following graphs is representing "live" stats data corresponding to the obtained above results
  • from the left to the right you can see 4 tests with the same MySQL 5.7, but configured with :
    • #1) sd6, ccr0
    • #2) sd6, ccr64
    • #3) sd96, ccr0
    • #4) sd96, ccr64
  • the first graph is showing reached Commit/sec rate (TPS)
  • the second one is the amount of concurrent user sessions
  • and the third graph is showing corresponding mutex/RW-locks spin waits reported by InnoDB :

Observations :
  • as you can see the default #1) case is hitting the highest lock contentions and reaching the lowest TPS..
  • tuning concurrency=64 in the case #2) is helping to lower waits on other locks, except log_sys, and also helps to avoid a TPS drop on a higher load..
  • tuning spin_delay=96 in case #3) lowering finally log_sys and giving us the highest TPS result here
  • adding concurrency=64 in case #4) lower spin waits yet more, but then the processing becomes "too relaxed", and TPS results is not better, while becomes more stable ;-))

While if we will go yet more in details about observed spin waits we may discover the following (adding CPU Usage% and Perf Profiler stats):

Observations :
  • well, just to show you that only once spin_delay was set to 96 we're starting to use CPU time fully..
  • however, we're spending 15%, 20%, or over 25% in the "sleeping" code (ut_delay())
  • and this is where our future potential gain is ;-))

Very hope the next MySQL/InnoDB version will get a rid of all these lock contentions and use HW way more efficiently.. -- let's see ;-))

Now, let's go back to the beginning of all this story (over 2 years ago), and get a look where we're finally today!

So far, just as a reminder, here are the results on OLTP_RO workload obtained on the all mentioned MySQL Engines on the same 72cores-HT server (and published before) :

Sysbench OLTP_RO 1M x 8-tables @72cores-HT (QPS) :

As you can see, MySQL 5.7 is reaching here 1M QPS, while MySQL 5.6 (and other "5.6 based") Engines are blocked around 400K QPS...

Now, what about OLTP_RW ?..

Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (QPS) :

Observations :
  • NOTE : this is OLTP_RW results with Engines configured with trx_commit=2 and dblwr=0, so the max possible OLTP_RW performance is reached here..
  • NOTE : the results are presented in QPS (and not TPS) to be "compatible" with OLTP_RO
  • so far MySQL 5.7 is reaching 800K QPS here, the best result from all Engines, and its OLTP_RW result is lower than 1M QPS OLTP_RO (as naturally should be "expected")
  • Percona Server 5.6 is on the second positions with its not far from 600K QPS, and way higher than its 400K QPS obtained on OLTP_RO..
  • the 3rd is MySQL 5.6, 500K QPS on OLTP_RW, while 400K QPS on OLTP_RO
  • 4th is MariaDB 10.1 with 450K QPS on OLTP_RW and higher result as well than on OLTP_RO..

So far, the OLTP_RO vs OLTP_RW target was finally reached by MySQL 5.7 only. Time for other challenges, work in progress ;-))

Let's now go back to OLTP_RW results more in details and see the impact of all tested configurations.

Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

MySQL 5.7 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

MySQL 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

MySQL 5.5 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

Percona Server 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

MariaDB 10.1 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=2 dblwr=0 (TPS) :

Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

MySQL 5.7 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

MySQL 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

MySQL 5.5 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

Percona Server 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

MariaDB 10.1 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=0 (TPS) :

Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

MySQL 5.7 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

MySQL 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

MySQL 5.5 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

Percona Server 5.6 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

MariaDB 10.1 Scalability @Sysbench OLTP_RW 1M x 8-tables @72cores-HT, config: trx_commit=1 dblwr=1 (TPS) :

From the presented above OLTP_RW results you can see that :
  • switching trx_commit=1 is giving the biggest impact on performance..
  • adding dblwr=1 here is not impacting too much due a relatively not too hard flushing involved by the tested workload (not too hard for the used flash storage)
  • with trx_commit=2 the absolute winner is MySQL 5.7
  • with trx_commit=1 on 72cores the winner is MySQL 5.7, while on 36cores is Percona Server 5.6 (small, but visible gain), and on 18cores rather MySQL 5.5 (surprise! ;-)) just that it has a drop on 1024 users
  • with trx_commit=1 + dblwr=1 the result is not much different from just trx_commit=1 :

  • there was a really huge gain made in scalability improvement in MySQL 5.7 !..
  • reaching over 40K TPS on OLTP_RW is the highest ever result I've seen on MySQL until now ;-)
  • however, there is yet more to do in MySQL for efficiency and further scalability improvements in RW workloads..
  • the main challenges are around REDO log management
  • while on heavy IO-bound RW workload the double_write becomes a huge problem as well (more about later, in the next articles)..
  • well, work in progress, stay tuned ;-))

As usually, any comments are welcome! And thank you for using MySQL! ;-))



The Sysbench command used to run OLTP_RW test via IP port (starting 8 processes in parallel):

$ LD_PRELOAD=/usr/lib64/libjemalloc.so /BMK/sysbench --num-threads=$1 \
        --test=oltp --oltp-table-size=1000000 \
        --oltp-dist-type=uniform --oltp-table-name=sbtest_1M_$n \
        --max-requests=0 --max-time=$2 --mysql-host= --mysql-port=5700 \
        --mysql-user=dim --mysql-password=dim --mysql-db=sysbench \
        --mysql-table-engine=INNODB  --db-driver=mysql \
        run  > /tmp/test_$n.log &

the my.conf I've used during the tests :

# general
  table_open_cache = 8000

# files

# buffers
  innodb_buffer_pool_size= 32000M

# tune
  innodb_doublewrite= 0 / 1 
  innodb_thread_concurrency=0 / 64
  innodb_flush_log_at_trx_commit=2 / 1
  innodb_stats_persistent = 1
  innodb_spin_wait_delay=6 / 96

# perf special
  innodb_adaptive_flushing = 1
  innodb_flush_neighbors = 0
  innodb_read_io_threads = 4
  innodb_write_io_threads = 4

# Monitoring
  innodb_monitor_enable = '%'

Posted by Dimitri at 13:23 - Comments...
Categories: MySQL

Friday, 11 December, 2015

MySQL Performance: Re:Visiting InnoDB vs MyISAM with MySQL 5.7

Next article from the MySQL 5.7 Performance stories (if missed, see 1.6M SQL Query/sec (QPS) with MySQL 5.7, 1M SQL Query/sec on mixed OLTP_RO , true Point-Selects performance and over 100K Connect/sec Rate -- all with MySQL 5.7)..

The today's article will be about re:visited MyISAM -vs- InnoDB performance comparison within MySQL 5.7 -- in fact the main and detailed article related to these engines comparison I've already published in 2012 but with MySQL 5.6 (just before MySQL 5.6 became GA) -- however, since then I'm constantly re:asked "And what about MySQL 5.7 ?" -- so, the following is the answer ;-))

First of all, let's summarize little bit what was already observed with MySQL 5.6 before :

  • so, on Full Text Search (FTS) InnoDB was already way better than MyISAM, no need to replay..
  • (on OLTP RW with its table-locking design MyISAM will always loose -vs- row-locking InnoDB, no need to waste a time either)
  • then, on mixed OLTP_RO workload : InnoDB was slightly, but better (215K QPS) -vs- MyISAM (200K QPS)
  • on Simple-Ranges queries workload : InnoDB was much better (170K QPS) -vs- MyISAM (95K QPS)
  • and on Point-Select queries workload : InnoDB was much worse (250K QPS) -vs- MyISQM (430K QPS)
    • NOTE: however, InnoDB was able to reach 450K QPS in experimental on that time "read_only mode", this showed the potential gain possible "in theory" to reach on InnoDB by by-passing the whole transactions layer, but not too much useful in real life (if writes are not allowed), so for MySQL 5.6 times it was more likely a hacking rather a real solution..
But since then, things are changed a lot with MySQL 5.7 :
  • the whole transactional layer was greatly improved in InnoDB
  • as well the whole MySQL Server code got a rid of all known scalability bottlenecks
  • so, we're having a much higher expectation to scale today with MySQL 5.7 than with 5.6 in the past ;-)

However, keeping this all in mind, it's not yet really clear if since then the gap between InnoDB and MyISAM was increased or decreased in MySQL 5.7 -- because general improvements in MySQL Server code made also MyISAM running faster.. -- and as usual, only a real test will give us a real answer ;-)

So far, this was the main reason to re:visit 3 years old obtained results, and my new results presented below are coming from the following :
  • HW config : 32cores-HT server (exactly the same I've used 3 years ago) and a newer 40cores-HT server (to observe a tendency)
  • OS : the same Oracle Linux 6.5
  • Test workloads :
    • load level : 8, 16, 32, .. 1024 concurrent user sessions
    • test cases: Sysbench OLTP_RO, RO Simple-Ranges, RO Distinct-Ranges, RO Point-Selects
    • datasets : single table with 10M rows, 8 tables with 1M rows each

And, finally, here are the results :

Mixed OLTP_RO workload

dataset 10M x 1-table @32cores-HT :

dataset 1M x 8-tables @32cores-HT :

dataset 10M x 1-table @40cores-HT :

dataset 1M x 8-tables @40cores-HT :

RO Simple-Ranges

dataset 10M x 1-table @32cores-HT :

dataset 1M x 8-tables @32cores-HT :

dataset 10M x 1-table @40cores-HT :

dataset 1M x 8-tables @40cores-HT :

RO Distinct-Ranges

dataset 10M x 1-table @32cores-HT :

dataset 1M x 8-tables @32cores-HT :

dataset 10M x 1-table @40cores-HT :

dataset 1M x 8-tables @40cores-HT :

RO Point-Selects

dataset 10M x 1-table @32cores-HT :

dataset 1M x 8-tables @32cores-HT :

dataset 10M x 1-table @40cores-HT :

dataset 1M x 8-tables @40cores-HT :

  • in MySQL 5.7 both InnoDB and MyISAM engines are giving better results than before on the same workloads and the same HW
  • all the results obtained on 40cores-HT server are better than on 32cored-HT
  • the most critical Point-Select workload is now leaving only a small gain to MyISAM -vs- InnoDB (and it's easy to understand - the overhead of transactions is still present in InnoDB, even if the code was greatly improved for scalability.. -- however, this is now nothing about hacking, but a true, production ready, re:designed code!)..
  • then, on all other test workloads - InnoDB is doing just better than MyISAM
  • while on all the tests using a single table - InnoDB is far way faster than MyISAM, even on Point-Selects

As usual, any comments are welcome! Thank you for using MySQL ! (and preparing your upgrade to MySQL 5.7 asap ;-))

MySQL 5.7 rocks! ;-)

Posted by Dimitri at 19:25 - Comments...
Categories: MySQL

Friday, 27 November, 2015

MySQL Performance: Improved Connect/sec Rate in MySQL 5.7

This article is continuing the MySQL 5.7 Performance story, started from 1.6M QPS on MySQL 5.7 details post , then 1M QPS on mixed OLTP_RO with MySQL 5.7 article, and detailed story about why the Point-Selects performance is so critical (and why the 1M result published by MariaDB is not fair)..

The current story will be about Connect/sec (connect/disconnect) performance improvement in MySQL 5.7 - such kind of metric is very critical for any application which cannot use persistent connections all the time (and many web apps are in such a case). Well, I'd say MySQL from the beginning was extremely good for its lightweight connections, and made in the past the base of success for many web solutions.. However, time is going, and we're no more with 4cores as "commodity hardware" (this is rather a smart-watch today ;-)) - so, there was a need to speed-up this Connect rate to match higher workloads. This was already greatly done in MySQL 5.6, and finally yet more improved in MySQL 5.7 - you may read all details about directly from our developers - I'll just present here a short summary about where we're today..

So far, first of all, how to test the Connect/sec performance of your MySQL server instance? - the most simple way here is just to use a standard Sysbench kit, load 10M rows into sysbench database (1 table or several tables, no matter -- the main show-stopper here is the Connect code itself), and then run the following :


# ----------------------------------------------------------------
# Connect/sec test
# ----------------------------------------------------------------

  for Users in 8 16 32 64 128 256 512 1024
    LD_PRELOAD=/usr/lib64/libjemalloc.so.1  sysbench --num-threads=$Users \
        --test=oltp --oltp-table-size=10000000 \
        --db-ps-mode=disable --oltp-dist-type=uniform --oltp-table-name=sbtest_10M \
        --max-requests=0 --max-time=300 --mysql-socket=/tmp/mysql.sock \
        --mysql-user=dim --mysql-password=dim --mysql-db=sysbench \
        --mysql-table-engine=INNODB  --db-driver=mysql \
        --oltp-point-selects=1 --oltp-simple-ranges=0 --oltp-sum-ranges=0 \
        --oltp-order-ranges=0 --oltp-distinct-ranges=0 --oltp-skip-trx=on \
        --oltp-read-only=on --oltp-reconnect-mode=query --oltp-connect-delay=0 run
    sleep 30

# ----------------------------------------------------------------

means on every point-select query your client session will re-connect, and the final QPS result will give you the max Connect/sec rate your MySQL instance is able to reach for a given amount of concurrent users.

And here are the results obtained from older to newer generations Intel-based Linux servers :

12cores-HT @2.9Ghz :

32cores-HT @2.3Ghz :

40cores-HT @2.3Ghz :

72cores-HT @2.5Ghz :

Instead of SUMMARY :

  • Connect/sec performance is mainly depending on the MySQL "connect/disconnect" code itself + CPU chip speed
  • it's hard to speak about "scalability" here as the max possible Connect/sec rate limit is reached pretty quickly and depending on IP stack performance as well..
  • tuning "thread_cache_size" to something bigger than zero is helping here, but not too much..
  • MySQL 5.7 showing the best performance here regardless the HW platform, and reaching over 100K Connect/sec on the latest Intel CPU chip
  • there is a clear better-and-better tendency in MySQL 5.5 => 5.6 => 5.7 results
  • and we still can do yet more better with MySQL 5.8 ! (question of time and resources - so, please, send us your feedback/ votes/ wishes if you want to see it ;-))

MySQL 5.7 rocks! ;-))


Posted by Dimitri at 18:15 - Comments...
Categories: MySQL

Wednesday, 11 November, 2015

MySQL Performance: What is odd with 1M QPS claimed by MariaDB 10.1 ?..

This article is continuing the MySQL 5.7 Performance story, started from 1.6M QPS details post, and followed by 1M QPS OLTP_RO article. However, the current story will not be mostly about MySQL 5.7, but also about announced on the same time MariaDB 10.1 GA ;-)

So far, MySQL Team was proud to show 1.6M QPS on Point-Select (SQL) queries, and MariaDB 10.1 GA announce was also claiming an ability to reach 1M QPS, also on Point-Selects, but on POWER8 HW. And I may be only happy for MariaDB team for their progress on POWER systems, except just one small detail related to how their 1M QPS result was obtained..

But first of all, what are these Point-Selects and what is so special with this workload ?..

  • point-select is representing a single SQL query reading a row by its primary key (PK)
  • a workload based on such queries is very similar to any generic key-value store solution, but via SQL
  • usually a point-select is extremely fast and doing a round-trip from end-to-end in database engine
  • so any internals overhead in engine code, any contentions, any scalability limits are seen very quickly..
  • historically such kind of workload did not scale very well on MySQL/InnoDB tandem..
  • on MySQL Server side there was a huge amount of internal locks around every SQL query execution
  • while on the InnoDB side there was a huge general overhead related to transactions management + related locks..
  • the first step ahead was made here in MySQL 5.6
  • but the real changes came only with MySQL 5.7 ;-)

So, our 1.6M QPS on Point-Selects with MySQL 5.7 we were able to reach under the most heavy conditions :
  • each Sysbench "client" thread is executing a single point-select query per iteration
  • no transactions clauses used, no grouping..
  • single query round-trip is driving the response time latency
  • a fair simulation of a key-value store by SQL access

and the Sysbench execution command line is looking then as the following:
LD_PRELOAD=/usr/lib64/libjemalloc.so /BMK/sysbench --num-threads=$1 \
        --test=oltp --oltp-table-size=1000000 \
        --oltp-dist-type=uniform --oltp-table-name=sbtest_1M_$n \
        --max-requests=0 --max-time=$2 --mysql-socket=/SSD_raid0/mysql.sock \
        --mysql-user=dim --mysql-password=dim --mysql-db=sysbench \
        --mysql-table-engine=INNODB  --db-driver=mysql \
        --oltp-point-selects=1 --oltp-simple-ranges=0 --oltp-sum-ranges=0 \
        --oltp-order-ranges=0 --oltp-distinct-ranges=0 --oltp-skip-trx=on \
        --oltp-read-only=on run  > /tmp/test_$n.log &

Now, about 1M QPS result published on MariaDB 10.1 :
  • if you'll look in details published in their article, instead of --oltp-point-selects=1 the --oltp-point-selects=1000 was used
  • and these 1K point-selects then grouped and executed within a single transaction!.. (--oltp-skip-trx=off is used (default))

Adapting these test conditions to my Sysbench command line this will then give the following :
LD_PRELOAD=/usr/lib64/libjemalloc.so /BMK/sysbench --num-threads=$1 \
        --test=oltp --oltp-table-size=1000000 \
        --oltp-dist-type=uniform --oltp-table-name=sbtest_1M_$n \
        --max-requests=0 --max-time=$2 --mysql-socket=/SSD_raid0/mysql.sock \
        --mysql-user=dim --mysql-password=dim --mysql-db=sysbench \
        --mysql-table-engine=INNODB  --db-driver=mysql \
        --oltp-point-selects=1000 --oltp-simple-ranges=0 --oltp-sum-ranges=0 \
        --oltp-order-ranges=0 --oltp-distinct-ranges=0 --oltp-skip-trx=off \
        --oltp-read-only=on run  > /tmp/test_$n.log &

How does this change the initial workload test case ?
  • in one word : completely ;-)
  • by grouping 1000 queries within a single transaction we're lowering a lot the whole related transaction locks..
  • and as the result, an overall QPS numbers are growing! ;-)
  • but did you see many real cases when a single MySQL session is grouping 1000 SELECT queries within a single transaction ?..
  • I may still imagine a need to run several SELECTs within a single transaction to guarantee a read consistency...
  • but such kind of queries are usually not short ones, so not really good to show a high QPS ;-)
  • but well, even they are really short as point-selects.. -- what kind of application will run them by 1000 in a single shot ?..
  • such kind of a "workaround" we proposed yet to our users when started to ship MySQL 5.6, but always mentioned that this is as a workaround, not a final solution (as this could help when you're really have many fast SELECTs and you can really group then within a single transaction without breaking your apps logic).. -- but as soon as potential amount of SELECTs to group is small, the transaction overhead is quickly eating your gain..
  • so, the real solution here is - MySQL 5.7 ;-)

Let me show now all this by example, using the test scenario as proposed by MariaDB and just vary the amount of point-selects executed within a single transaction. Let's start with 50 point-selects (which is already too much as to me, but well) :

50 point-selects in transaction :

Observations :
  • MySQL 5.7 is still reaching its 1.6M QPS as well
  • MariaDB 10.1 is reaching over 1.4M QPS (so, not only on Power while running within a "workaround" test conditions)..

Then the following are the results with 25, 10, and 5 point-selects executed within the same transaction :

25 point-selects in transaction :

10 point-selects in transaction :

5 point-selects in transaction :

Observations :
  • as you can see, less queries executed within the same single transaction - lower QPS is reached..
  • so, MySQL 5.7 is going from 1.6M QPS to 1.2M QPS
  • while MariaDB 10.1 is going from 1.4M QPS to just 600K QPS..

On the last test, with 5 point-selects within a transaction the lower QPS is also impacted by round-trips of BEGIN and COMMIT statements around transaction.. What the result will be if I'll not use transactions?

5 point-selects without transaction :

Observations :
  • as you can see, MySQL 5.7 is going back to its 1.6M QPS
  • while MariaDB 10.1 is going yet more down to just slightly higher than 400K QPS only..

To get a better understanding of the transaction statements impact let's get a look on the following graph comparing MySQL 5.7 in the last test with 5 point-selects within transaction (left side) -vs- 5 point-selects without transaction (right side) :

Observations :
  • as you can see in overall amount of Queries/sec the left side is even higher! (BEGIN and COMMIT are also counted as queries by MySQL stats)
  • and as we're wasting CPU cycles to process BEGIN and COMMIT - we're doing less SELECTs as the result..
  • while on the right side (without transactions) the whole CPU time is spent for SELECTs, and we're reaching 1.6M QPS then ;-)

Now :
  • it's up to you to consider whenever MariaDB 10.1 is really reaching 1M QPS, or 400K QPS only ;-))
  • however, what is important for me here after all : you can really reach 1.6M QPS with MySQL 5.7 whatever the test conditions are used here ;-))

Then, to avoid any kind of speculations about new Intel chips as the reason of excellent MySQL 5.7 scalability results, let me just remind you about the results obtained on the old severs (32cores-HT and 40cores-HT), running the old Intel CPUs (similar 4CPU sockets each, but just 8cores-HT and 10cores-HT per CPU socket, both are running at 2300Mhz frequency). The following are the results obtained on the same Sysbench RO Point-Select workload :
  • single point-select per iteration, no transactions
  • 8 tables of 1M rows are used in the first test
  • 1 table of 10M rows is used in the second test

32cores-HT :

40cores-HT :

72cores-HT :

Observations :
  • as you can see there is a huge gap between MySQL 5.7 and any other engine on 32, 40 and 72cores-HT HW..
  • the gap on 72cores-HT HW is way bigger only because MySQL 5.7 is continuing to scale and reaching a yet more higher result, while all other engines are already reached their limits and cannot go anymore further..
  • NOTE : only MySQL 5.7 is showing near the same QPS results on both 8-tables and 1-table workloads

  • From where is coming such a great scalability gain in MySQL 5.7 ?
    • first of all it's a continuous improvement process started yet since MySQL 5.6 with kernel_mutex split + RO transactions on InnoDB side, and many various internal contentions improvements on the MySQL Server side
    • then, on MySQL 5.7 InnoDB side : a whole transactions management redesign, improved lock management, redesigned index locking, etc...
    • MySQL 5.7 Server side : resolved contentions around MDL, THR_lock, LOCK_grant, LOCK_plugin, and all other "next-level" locks fixes.. -- in fact for today there is no more any known/visible internal contentions in MySQL 5.7 except coming from InnoDB ;-)
    • so far, all the credit is to our great MySQL Engineering Team! (all the listed stuff above is related to fundamental changes invented and implemented by our Engineering, taking us months and years of heavy work)..
    • and, of course, huge thanks to MySQL Community for all feedback we have about ;-)

  • When MariaDB will be able to scale as far as MySQL 5.7 ?
    • when it'll move to InnoDB SE from MySQL 5.7
    • and when on its Server side the lock contention in the "lock free" table definition cache code will be fixed ;-)

  • When Percona Server will scale as far as MySQL 5.7 ?
    • since Percona Server will move to the MySQL 5.7 code base
    • and XtraDB moves to InnoDB code base from MySQL 5.7
    • not before ;-)

  • or both are re:implementing all these changes in their 5.6 / 10.1 code ;-)
  • And hope I don't say you here any news, because the same story was already with MySQL 5.6 too, but who cares? ;-))

Well, what to say.. -- #MySQL 5.7 rocks! ;-)


Posted by Dimitri at 2:12 - Comments...
Categories: MySQL

Friday, 06 November, 2015

Slides from my talk about MySQL Performance @OpenWorld 2015

Slides from my talk during MySQL Central @OpenWorld 2015 are available from here now :
- http://dimitrik.free.fr/Presentations/MySQL_Perf-Tuning-OOW2015-dim.pdf 

they should be soon available from the OpenWorld site as well.


Posted by Dimitri at 20:33 - Comments...
Categories: MySQL

Thursday, 05 November, 2015

MySQL Performance: 1M QPS on mixed OLTP_RO with MySQL 5.7 GA

This article is following the MySQL 5.7 Performance series started from 1.6M QPS details post

Let's focus now on the Sysbench "mixed" OLTP_RO workload (so, not only Point-Selects, but all RO queries as it was initially designed in OLTP_RO scenario in Sysbench), which is composed of :

  • x10 point-selects
  • x1 simple-ranges
  • x1 order-ranges
  • x1 sum-ranges
  • x1 distinct-ranges

Note about test conditions :
  • in this and in the previous article we're seeking for MySQL & InnoDB scalability limits ;-)
  • so, yes, the client and server are running locally on the same host (we're not testing here network stuff vendors)
  • the load is not IO-bound either, very quickly the whole dataset is reaching BP and remains in memory (we're not testing IO vendors here)
  • again, all the focus here is on MySQL scalability limits, nothing else..

Note about tested workloads :
  • why we're paying so many attention to these "simple" queries from Sysbench ?..
  • well, just consider it like the "entry ticket" for any database engine ;-)
  • these simple tests in fact are extremely aggressive, and bombarding all engine internals very heavily..
  • the point-select, for ex., is extremely fast and crossing on every pass the whole engine stack from entry to end point & back..
  • while the distinct-ranges is extremely aggressive on malloc() scalability + in-memory temp tables management..
  • etc. etc. etc..
  • so, if your production workload is based on much more complex queries, and you're suspecting scalability issues -- rather to stay negative, send us your test workload and share your observations -- we cannot improve everything within a one single shot, right? -- there is still so many things to do yet..
  • but I just may say you one thing : without improved scalability on "simple" loads any "complex" load scalability is just impossible.. -- so, stay tuned, we're coming ;-)

Note about the tested HW :
  • I was told several times during the MySQL Central conference and other user meeting that 72cores config is waaay toooo big..
  • guys, is it really big ?? ;-)
  • just think that this is the same 4CPU sockets server as we used before..
  • just that today's Intel chip has 18cores per socket -vs- 10cores we saw before, and the CPU chip itself was also greatly improved..
  • well, if 4CPU is still toooo biiiig for you, will be 2CPU is "good enough" ?..
  • but even with 2CPU you're having 36cores-HT here ;-)
  • and this 2CPU 36cores-HT config is already showing a way better QPS than we observed on 4CPU 40cores-HT before !!
  • what to do with this then ?? ;-)
  • keeping in mind that the next Intel chip will give you 48cores-HT (24cores-HT per CPU socket)..
  • so, you want it, or not -- scalability is THE MUST today to give MySQL users a full power of their HW ;-))

Well, a long story short, let's go directly to the test results.

Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

Observations :
  • MySQL 5.7 is reaching 1M QPS on OLTP_RO !! (while seems like there is still a room for progress)..
  • on the second position is MySQL 5.6, and in max-to-max comparison MySQL 5.7 is doing x2.5 times better than 5.6
  • Persona Server 5.6 is taking #3position
  • and, surprisingly MariaDB 10.1 here the worse, except MySQL 5.5
  • Note that except MySQL 5.7, the difference between MySQL 5.5 result and other engines is not that big..
  • this is because QPS gain here is coming for them mostly from "mixed" ranges queries, which was already not that bad in 5.5
  • (and if you payed attention to the previous article, you may see that on point-selects MySQL 5.5 is reaching the same max QPS as all other engines, except 5.7)..
  • so, yes, the huge gain you're seeing here for MySQL 5.7 is coming due all this heavy remastering started from TRX-list re-design 2 years ago and continued on all levels till 5.7 GA release..
  • indeed, this was not easy, but yes, we done it !!! ;-))

What about scalability now?

MySQL 5.7 Scalability @Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

MySQL 5.6 Scalability @Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

MySQL 5.5 Scalability @Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

Percona Server 5.6 Scalability @Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

MariaDB 10.1 Scalability @Sysbench OLTP_RO 1M x 8-tables 72cores-HT :

Observations :
  • only MySQL 5.7 is really scaling here up to 72cores-HT
  • except MySQL 5.5, all other engines are having better QPS on 32cores-HT -vs- 18cores-HT
  • however, this gain is not that big.. - but MySQL 5.6 is doing better than others
  • MariaDB 10.1 is the worse again, just better than the oldest MySQL 5.5..

Now the same workload, but using only a single 10M rows table.

Sysbench OLTP_RO 10M x 1-table 72cores-HT :

Observations :
  • MySQL 5.7 is the best again, but not yet reaching 1M QPS, a room for improvement ;-)
  • MySQL 5.6 and Percona Server 5.6 on the #2 position
  • and MariaDB 10.1 closing the group, just before MySQL 5.5

And scalability?

MySQL 5.7 Scalability @Sysbench OLTP_RO 10M x 1-table 72cores-HT :

MySQL 5.6 Scalability @Sysbench OLTP_RO 10M x 1-table 72cores-HT :

MySQL 5.5 Scalability @Sysbench OLTP_RO 10M x 1-table 72cores-HT :

Percona Server 5.6 Scalability @Sysbench OLTP_RO 10M x 1-table 72cores-HT :

MariaDB 10.1 Scalability @Sysbench OLTP_RO 10M x 1-table 72cores-HT :

Observations :
  • the result is very similar to 8-tables results, except that Percona Server 5.6 is very close with MySQL 5.6 here
  • while MySQL 5.7 is just the best ;-)

And, similar to the previous article, here are the results reflecting the evolution of tested HW and CPU power :

MySQL 5.7 Scalability @Sysbench OLTP_RO 1M x 8-tables :

MySQL 5.7 Scalability @Sysbench OLTP_RO 10M x 1-table :

Indeed, the difference is very impressive ;-)

Over last 2 weeks in all discussions I've got many times the same question : do we really need to upgrade our HW to get the best from MySQL Performance ?...

Let me show you then just few following graphs :

here is HW evolution related to MySQL 5.5 on OLTP_RO the presented workload :

Observations :
  • as you can see, 5.5 was the best on 12cores-HT config on the old HW
  • it was not able to show anything better on 32 or 40cores-HT configuration..
  • however, moved to the newer CPU chip, even MySQL 5.5 is going x2 times faster here! ;-)
  • and as you can see from the 5.5 scalability graphs, 1CPU socket is just enough here..
  • and, unfortunately, 1CPU will be also your limit for MySQL 5.5 Performance ;-)

now the same for MySQL 5.6 :

Observations :
  • MySQL 5.6 is scaling better, and already able to show over 50% better performance on an old, but bigger HW
  • but on the newer CPU it's doing yet x2 times better (even without scaling well)..

And, of course, once you'll move to MySQL 5.7, you'll be able to go yet more far on these new 2CPU or 4CPU sockets :

Observations :
  • no comments ;-))

And to finish, few more details about the test conditions :

my.conf -- used exactly the same config settings as in the previous article.

The Sysbench command used to run OLTP_RO test via IP port (starting 8 processes in parallel):
$ LD_PRELOAD=/usr/lib64/libjemalloc.so /BMK/sysbench --num-threads=$1  \
        --test=oltp --oltp-table-size=1000000 \
        --oltp-dist-type=uniform --oltp-table-name=sbtest_1M_$n \
        --max-requests=0 --max-time=$2 --mysql-host= --mysql-port=5700 \
        --mysql-user=dim --mysql-password=dim --mysql-db=sysbench \
        --mysql-table-engine=INNODB  --db-driver=mysql  --oltp-skip-trx=on \
        --oltp-read-only=on run  > /tmp/test_$n.log &

Should I say once more again MySQL 5.7 rocks !!! ;-))

Posted by Dimitri at 18:32 - Comments...
Categories: MySQL