DimitriK's (dim) Weblog

Last year we already published our over 2.1M QPS record with MySQL 8.0 -- it was not yet GA on that moment and the result was obtained on the server with 4CPU Sockets (4S) Intel Broadwell v4. We did not plan any improvement in 8.0 for RO related workloads, and the main target of this test was to ensure there is NO regressions in the results (yet) comparing to MySQL 5.7 (where the main RO improvements were delivered). While for MySQL 8.0 we mostly focused our efforts on lagging WRITE performance in MySQL/InnoDB, and our "target HW" was 2CPU Sockets servers (2S) -- which is probably the most widely used HW configuration for todays MySQL Server deployments..

However, not only SW, but also HW is progressing quickly these days ! -- and one of my biggest surprises last time was about Intel Skylake CPU ;-)) -- the following graph is reflecting the difference between similar 2S servers, where one is having the "old" 44cores-HT Broadwell v4, and another the "new" 48cores-HT Skylake CPUs :

the difference is really impressive, specially when you see that just on 32 users load (when CPU is not at all saturated not on 44cores nor 48cores) there is already 50% gain with Skylake ! (and this is about a pure "response time"), and on peak QPS level it's over 1.8M QPS (not far from 80% gain over Brodawell)..

And this results is marking our next milestone in MySQL RO performance on 2S HW ! ;-))

Year is finishing, and as a kind of "end-of-year" gift, I'm happy to announce that a freshy new CoreUpdate-17-12 is available from now ! ;-))

IMPORTANT : this is a very "sensible" update, and you cannot just to apply it on the top of already deployed dim_STAT instance as before.. -- there was a need to fix several issues within "under hood" binaries to make the new stuff working properly, so the new code has simply no chances to work with old binaries.. So far, I decided to make it all as a "single shot move" -- align a new update shipment with a moving to "64bit" versions support only :

• e.g. this is not a new version of dim_STAT
• this is just a "remastered" 64bit release + several visible and internal fixes
• any 32bit releases are remained "as it", and it makes no more sense to continue to support them..
• 64bit versions of dim_STAT v.9.0 are available for Linux and MacOSX (macOS)
• any further CoreUpdate will work only with 64bit version having the latest supported binaries..

well, this is just a snapshot, but hope you already can get an idea about how much "more clean" your graphs could be ;-))

This post is following the story of MySQL 8.0 Performance & Scalability started with article about 2.1M QPS obtained on Read-Only workloads. The current story will cover now our progress in Read-Write workloads..

Historically our Read-Only scalability was a big pain, as Read-Only (RO) workloads were often slower than Read-Write (sounds very odd: "add Writes to your Reads to go faster", but this was our reality ;-)) -- and things were largely improved here since MySQL 5.7 where we broke 1M QPS barrier and reached 1.6M QPS for the first time. However, improving Writes or mixed Read+Writes (RW) workloads is a much more complex story..

What are the main scalability show-stoppers in MySQL 5.7 and current 8.0 release candidate for RW and IO-bound workloads? - the most "killing" are the following ones :

• REDO log contentions are blocking your whole transaction processing from going faster..
• Transaction (TRX) management becomes very quickly a huge bottleneck as soon as your transactions are fast and/or short..
• internal locking and row locking (LOCK) will quickly kill your performance as soon as your data access pattern is not uniform, etc..
• and yet more, historically as soon as you're involving any IO operations, they all will go via one single and global locking path (fil_system mutex) which will make a use of faster storage solutions (flash) simply useless..

The whole story about is pretty amazing, but I have to be short, so :

• in short : we know exactly what we have to do to get a rid of this all
• we have a working prototype code allowing us to expect pretty important potential gains in RW and pure Write workloads
• the only real problem here is that a road from "prototype" to "production quality" code is much longer than anyone could expect (even me ;-))
• so within MySQL 8.0 GA timeframe we could not deliver all the fixes we have, and we have to go by priority here..
• and the priority #1 from the list of issues mentioned above is for sure going to REDO and IO problems, as the most common show-stoppers for most of RW workloads today
• the 8.0 planned changes are not yet final, but you may already get a first idea about by trying our "preview" MySQL 8.0-labs release

The first release candidate of MySQL 8.0 is here, and I'm happy to share few performance stories about. This article will be about the "most simple" one -- our in-memory Read-Only performance ;-))

However, the used test workload was here for double reasons :

• 1) validate MySQL 8.0 performance
• 2) fully evaluate the "New" Sysbench developed by Alex (https://github.com/akopytov/sysbench)

Going ahead to the second point, the main worry about New Sysbench was about its LUA overhead (the previous version 0.5 was running slower than the old one 0.4 due LUA) -- a long story short, I can confirm now that the New Sysbench is running as fast as the oldest "most lightweight" Sysbench binary I have in use ! so, KUDOS Alex !!! ;-))

While regarding the improvements coming with MySQL 8.0 on Read-Only workloads I'd mention :

• several "overheads" were fixed
• the most notable one is related to UTF8, of course
• however, even latin1 related functions were improved little bit
• but this was only about "overheads", and nothing about "scalability"
• because the main "scalability" gap was already made with MySQL 5.7 two years ago ;-))
• so, our main merit with MySQL 8.0 here will be rather NOT TO LOOSE the already obtained gain !
• (agree, sounds very odd, but if you'll just look on the list of the all new features coming with 8.0 you can imagine our code path is not going to be shorter, right ? ;-))
• so the fair test here will be to compare 8.0 vs 5.7 and 5.6 with latin1 encoding
• (for UTF8 the winner is 8.0 and from very far, which you already know)

The most "sensible" RO workload in Sysbench is Point-Selects, so here is my test scenario:

• workload : New Sysbench RO point-selects
• data volume : 8 tables of 10M rows each
• encoding : latin1
• user load levels : 1, 2, 4, .. 1024
• engines : MySQL 8.0, MySQL 5.7, MySQL 5.6
• server : 96cores-HT 4CPU sockets 2.2Ghz (Broadwell), OL7.3

and here is the result :

Observations :

• 2.1M SQL Query/sec for MySQL 8.0 -- our current new Max QPS record obtained in MySQL history !
• which is great, no doubt !
• however, there is a clearly seen small, but visible QPS regression on lower load levels..
• which is not really cool (even if could be easily explained by increased code path + new DD + etc.. etc..)
• well, adding it to my list of "low load" performance issues and will investigate later..

Read more...

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 ;-)