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https://issues.apache.org/jira/browse/HBASE-21721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17163054#comment-17163054
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Michael Stack commented on HBASE-21721:
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{quote}As I read this change, if a difference between highestUnsyncedSequence
and currentSequence post-sync, then the syncfutures inside this difference will
be released but their sync may not have come in so yes, less syncs but our
accounting will be off.
{quote}
I see now how it could make a sync cover more edits; my bad (I read
[~anoop.hbase] 's comments in PR... that helped).
Looking at AsyncFSWAL, it does the math differently so this does not apply
there.
If an update, could test and apply; would help older hbases. Thanks.
> reduce write#syncs() times
> --------------------------
>
> Key: HBASE-21721
> URL: https://issues.apache.org/jira/browse/HBASE-21721
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 1.3.1, 2.1.1, master, 2.2.3
> Reporter: Bo Cui
> Priority: Major
>
> the number of write#syncs can be reduced by updating the
> highestUnsyncedSequence：
> before write#sync(), get the current highestUnsyncedSequence
> after write#sync, highestSyncedSequence=highestUnsyncedSequence
>
> {code:title=FSHLog.java|borderStyle=solid}
> // Some comments here
> public void run()
> {
> long currentSequence;
> while (!isInterrupted()) {
> int syncCount = 0;
> try {
> while (true) {
> ...
> try {
> Trace.addTimelineAnnotation("syncing writer");
> long unSyncedFlushSeq = highestUnsyncedSequence;
> writer.sync();
> Trace.addTimelineAnnotation("writer synced");
> if( unSyncedFlushSeq > currentSequence ) currentSequence =
> unSyncedFlushSeq;
> currentSequence = updateHighestSyncedSequence(currentSequence);
> } catch (IOException e) {
> LOG.error("Error syncing, request close of WAL", e);
> lastException = e;
> } catch (Exception e) {
> ...
> }
> }
> {code}
> Add code
> long unSyncedFlushSeq = highestUnsyncedSequence;
> if( unSyncedFlushSeq > currentSequence ) currentSequence = unSyncedFlushSeq;
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