[jira] [Commented] (HBASE-15158) Change order in which we do write pipeline operations; do all under row locks!

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

    [ https://issues.apache.org/jira/browse/HBASE-15158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15125748#comment-15125748 ] 

stack commented on HBASE-15158:
-------------------------------

Preamble 1, HBASE-15186 was committed. The second preamble is HBASE-15196. It is second and last)piece broken out of this patch.

Hopefully the patch we have left over is 'only' 70k or so... and just a class or two to review. Let me get some cluster tests in here too before posting patch for review.

> Change order in which we do write pipeline operations; do all under row locks!
> ------------------------------------------------------------------------------
>
>                 Key: HBASE-15158
>                 URL: https://issues.apache.org/jira/browse/HBASE-15158
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Performance
>            Reporter: stack
>            Assignee: stack
>             Fix For: 2.0.0
>
>         Attachments: 15158.patch, 15158v2.patch
>
>
> Change how we do our write pipeline. I want to do all write pipeline ops under row lock so I lean on this fact fixing performance regression in check-and-set type operations like increment, append, and checkAnd* (see sibling issue HBASE-15082).
> To be specific, we write like this now:
> {code}
> # take rowlock
> # start mvcc
> # append to WAL
> # add to memstore
> # let go of rowlock
> # sync WAL
> # in case of error: rollback memstore
> {code}
> Instead, write like this:
> {code}
> # take rowlock
> # start mvcc
> # append to WAL
> # sync WAL
> # add to memstore
> # let go of rowlock
> ... no need to do rollback.
> {code}
> The old ordering was put in place because it got better performance in a time when WAL was different and before row locks were read/write (HBASE-12751).
> Testing in branch-1 shows that a reordering and skipping mvcc waits gets us back to the performance we had before we unified mvcc and sequenceid (HBASE-8763). Tests in HBASE-15046 show that at the macro level using our usual perf tools, reordering pipeline seems to cause no slowdown (see HBASE-15046). A rough compare of increments with reordered write pipeline seems to have us getting back a bunch of our performance (see tail of https://issues.apache.org/jira/browse/HBASE-15082?focusedCommentId=15111703&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15111703 and subsequent comment).



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