[jira] [Created] (IGNITE-7820) Investigate and fix perfromance drop of WAL for default mode

["Andrey Gura (JIRA)" <ji...@apache.org>]

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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