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Tuesday, 08 May, 2018

MySQL Performance : 8.0 and Sysbench OLTP_RW / Update-NoKEY

This post is following previously published OLTP_RO results for MySQL 8.0 (latin1 and utf8mb4 charsets), and now is focusing on Sysbench RW workloads, particularly "mixed" OLTP_RW and Update-NoKey :

  • OLTP_RW : while this workload has writes, it's mainly driven by reads (OLTP_RO + 2 updates + delete + insert)
  • Update-NoKey : aggressively bombarding UPDATE queries (but with no changes on indexed columns)
The same 2S Skylake server was used as in previous tests :

Server configuration :
  • OS : Oracle Linux 7.4
  • CPU : 48cores-HT Intel Skylake 2.7Ghz (2CPU sockets (2S), Intel(R) Xeon(R) Platinum 8168 CPU)
  • RAM: 172GB
  • Storage : x2 Intel Optane flash drives (Intel (R) Optane (TM) SSD P4800X Series)
    • volume : RAID-0 via MDADM
    • filesystem : EXT4
And I'm following mostly the same test conditions as previously explained for MySQL 5.7 GA -- similar variations in options (spin delay = 6;24;96 / thread concurrency = 0;64;128 / taskset = 1S/2S, etc.) to let each Engine to show its best possible TPS/QPS results.

However, as running the test with all these config variations is taking a significant time, I've slightly reduced the scope of investigation to the following :
  • trx_commit = 1 : along with our work on InnoDB REDO re-design we not only fixed the biggest related bottleneck, but also discovered and partially fixed several other issues around REDO (also mostly historical, but still) -- keeping all this in mind, I'd rather suggest you today to use "1" (flushing REDO log on COMMIT) whenever possible -- specially that with all the progress we're seeing on HW/Storage improvement last years -- the penalty of "1" with 8.0 becomes much less dramatic than before -vs- "2" (flush REDO log once per second), and also a big enough total size for the whole REDO space (currently I'm using x16 or x32 log files of 1GB each), more about later..
  • PFS = off : I'm intentionally now switching Performance Schema OFF just because it's not a bottleneck, but a pure "overhead" (as many other things as well) -- my main target in all benchmark investigations is "to see what is our next bottleneck", and as HW resources are always limited, any additional overhead will help to "hide" the real problem.. While PFS overhead is part of MySQL QA testing, and every overhead higher than 5% for "default instrumentation" is considered as a bug (mind to file a bug if you see it bigger in your case!) -- while from the other side many users are asking to see more an more instrumentation enabled by default regardless overhead (and this "balance" between overhead and benefit from built-in instrumentation is generally can be observed only case by case).
  • Checksums = off : this is also a pure "overhead" and not a bottleneck, while since CRC32 is supported, generally you'll not hit any problem..
  • Charset = latin1 : while most of interest is moving to UTF8, I'm continuing to test with "latin1" for the same reasons as UTF8 -vs- latin1 "overhead" which may hide you more important problems (while using UTF8 in 8.0 is giving you a direct gain -vs- any previous MySQL release, but I'm rather looking to point on problems than hide them)..
  • DoubleWrite = off : this, however, is a big problem and a big bottleneck, but the fix was already developed by Sunny since 2 years now, we worked on this together, and I can confirm you you'll not see any TPS drop as soon as your storage is able to follow (as you "writing twice", e.g. x2 times more) -- but the code is still NOT part of 8.0 because "there is always something more important to do" ;-)) -- please feel free to urge Sunny to push re-designed DoubleWrite code to 8.0 asap !! (Sunny's twitter : @sunbains) -- while for my part I need to see "what is after" once the new code is delivered..
  • Binlog = off : this is another big problem, and on the same time both bottleneck and overhead.. -- but this one rather need a very particular attention, so I'll skip it here to say you more later..

The full list of all config options you may always find at the end of the article, while here are the final results :

Sysbench OLTP_RW 10Mx8-tables TPS

Comments :
  • over 45K TPS with MySQL 8.0 !
  • around 35K TPS with MySQL 5.7 -- interesting that similar result was obtained in the past with 5.7 on 4S 72cores-HT Broadwell server, and now 2S Skylake 48cores-HT is just enough to get the same ;-))
  • NOTE : and we're still far from the max possible TPS to get from this HW ! => work in progress..
While looking on the same result expressed in QPS we can see that we're more and more close to 1M QPS obtained on the same server with pure OLTP_RO :

Sysbench Update-NoKey TPS

Comments :
  • near 250K TPS with MySQL 8.0 !
  • and indeed, there was a huge performance drop in 5.7 comparing to 5.6
  • extremely happy to see this fixed finally with 8.0 ;-))
  • (and no idea what to advice to MariaDB who just adopted InnoDB from 5.7)...

Then, for those who are curious about "overheads", the same test results but only for MySQL 8.0 with turned PFS=on and checksums=crc32 :

Update-NoKey :
As you can see, the difference is really small and remains under 5% (in case you expected to see something more big here ;-))

However :
  • even the results with MySQL 8.0 are looking better, we're yet far from scaling on Writes !
  • work is still in progress..

the full list of configuration options I've used :
# general max_connections=4000 table_open_cache=8000 table_open_cache_instances=16 max_prepared_stmt_count=512000 back_log=1500 default_password_lifetime=0 default_authentication_plugin=mysql_native_password character_set_server=latin1 collation_server=latin1_swedish_ci skip-character-set-client-handshake ssl=0 performance_schema=OFF skip_log_bin=1 transaction_isolation=REPEATABLE-READ # files innodb_file_per_table innodb_log_file_size=1024M innodb_log_files_in_group=32 innodb_open_files=4000 # buffers innodb_buffer_pool_size=128000M innodb_buffer_pool_instances=16 innodb_log_buffer_size=64M # tune innodb_doublewrite=0 innodb_thread_concurrency=0 innodb_flush_log_at_trx_commit=1 innodb_max_dirty_pages_pct=90 innodb_max_dirty_pages_pct_lwm=10 join_buffer_size=32K sort_buffer_size=32K innodb_use_native_aio=1 innodb_stats_persistent=1 innodb_spin_wait_delay=6 innodb_max_purge_lag_delay=300000 innodb_max_purge_lag=0 innodb_flush_method=O_DIRECT innodb_checksum_algorithm=none innodb_io_capacity=10000 innodb_io_capacity_max=40000 innodb_lru_scan_depth=9000 innodb_change_buffering=none innodb_read_only=0 innodb_page_cleaners=16 innodb_undo_log_truncate=off # perf special innodb_adaptive_flushing=1 innodb_flush_neighbors=0 innodb_read_io_threads=16 innodb_write_io_threads=16 innodb_purge_threads=4 innodb_adaptive_hash_index=0 # monitoring innodb_monitor_enable='%'

And if you wish to reproduce the same tests, you can find the MySQL 8.0 starter note here, and test related instructions from here and then here.

Thank you for using MySQL !


Posted by Dimitri at 3:37
Categories: MySQL
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