Andrey Gura created IGNITE-7820:
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Summary: Investigate and fix perfromance drop of WAL for default
mode
Key: IGNITE-7820
URL: https://issues.apache.org/jira/browse/IGNITE-7820
Project: Ignite
Issue Type: Bug
Affects Versions: 2.4
Reporter: Andrey Gura
Fix For: 2.5
WAL performance drop was introduced by
https://issues.apache.org/jira/browse/IGNITE-6339 fix. In order to provide
better performance for {{DEFAULT}} WAL mode
{{FsyncModeFileWriteAheadLogManager}} implementation was added as result of fix
issue https://issues.apache.org/jira/browse/IGNITE-7594.
What we know about this performance drop:
* It affects {{IgnitePutAllBenchmark}} and {{IgnitePutAllTxBenchmark}} and
measurements show 10-15% drop and ~50% drop accordingly.
* It is reproducible not for all hardware configuration. That is for some
configuration we see only performance improvements instead of drop.
* It is reproducible for [Many clients --> One server] topology.
* If {{IGNITE_WAL_MMAP == false}} then we have better performance.
* If {{fsyncDelay == 0}} then we have better performance.
What were tried during initial investigation:
* Replacing of {{LockSupport.park/unpark}} to spin leads to improvement about
2%.
* Using {{FileWriteHandle.fsync(null)}} (unconditional flush) instead of
{{FileWriteHandle.fsync(position)}} (conditional flush) doesn't affect
benchmarks.
What should we do:
Investigate the problem and provide fix or recommendation for system tuning.
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