[jira] [Created] (IGNITE-8057) Execute WAL fsync preventively before checkpoint begin

["Ivan Rakov (JIRA)" <ji...@apache.org>]

Ivan Rakov created IGNITE-8057:
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             Summary: Execute WAL fsync preventively before checkpoint begin
                 Key: IGNITE-8057
                 URL: https://issues.apache.org/jira/browse/IGNITE-8057
             Project: Ignite
          Issue Type: Improvement
    Affects Versions: 2.5
            Reporter: Ivan Rakov


After fix of IGNITE-7754, we execute explicit WAL fsync on checkpoint begin:
{noformat}
if (hasPages) {
    assert cpPtr != null;

    tracker.onWalCpRecordFsyncStart();

    // Sync log outside the checkpoint write lock.
    cctx.wal().flush(cpPtr, true);

    tracker.onWalCpRecordFsyncEnd();
{noformat}
It's executed outside of checkpoint write lock. However, it still can decrease overall throughput by suspending writing of dirty pages by checkpoint threads.
We can decrease time of this fsync by executing it preemptevely, before acquiring checkpoint write lock. 
We should prioritize this ticket if value of walCpRecordFsyncDuration metric in "Checkpoint started" message will be too big.
Note: it's possible to give a fsync hint to WAL manager in single-writer mode.



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