Horton

Re: Speed up Clog Access by increasing CLOG buffers

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, Dilip Kumar <dilipbalaut@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-12-05T02:14:05Z
Lists: pgsql-hackers 
On Mon, Dec 5, 2016 at 6:00 AM, Haribabu Kommi <kommi.haribabu@gmail.com> wrote:
>
>
> On Fri, Nov 4, 2016 at 8:20 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>>
>> On Thu, Nov 3, 2016 at 8:38 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> > On Tue, Nov 1, 2016 at 11:31 PM, Tomas Vondra
>> >> The difference is that both the fast-path locks and msgNumLock went
>> >> into
>> >> 9.2, so that end users probably never saw that regression. But we don't
>> >> know
>> >> if that happens for clog and WAL.
>> >>
>> >> Perhaps you have a working patch addressing the WAL contention, so that
>> >> we
>> >> could see how that changes the results?
>> >
>> > I don't think we do, yet.
>> >
>>
>> Right.  At this stage, we are just evaluating the ways (basic idea is
>> to split the OS writes and Flush requests in separate locks) to reduce
>> it.  It is difficult to speculate results at this stage.  I think
>> after spending some more time (probably few weeks), we will be in
>> position to share our findings.
>>
>
> As per my understanding the current state of the patch is waiting for the
> performance results from author.
>

No, that is not true.  You have quoted the wrong message, that
discussion was about WALWriteLock contention not about the patch being
discussed in this thread.  I have posted the latest set of patches
here [1].  Tomas is supposed to share the results of his tests.  He
mentioned to me in PGConf Asia last week that he ran few tests on
Power Box, so let us wait for him to share his findings.

> Moved to next CF with "waiting on author" status. Please feel free to
> update the status if the current status differs with the actual patch
> status.
>

I think we should keep the status as "Needs Review".

[1] - https://www.postgresql.org/message-id/CAA4eK1JjatUZu0%2BHCi%3D5VM1q-hFgN_OhegPAwEUJqxf-7pESbg%40mail.gmail.com


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Use group updates when setting transaction status in clog.

  2. Improve 64bit atomics support.

  3. Add ProcArrayGroupUpdate wait event.

  4. Make the different Unix-y semaphore implementations ABI-compatible.

  5. Fix broken ALTER INDEX documentation

  6. Code and docs review for commit 3187d6de0e5a9e805b27c48437897e8c39071d45.

  7. Partition the freelist for shared dynahash tables.

  8. Correct StartupSUBTRANS for page wraparound

  9. Make idle backends exit if the postmaster dies.

  10. contrib/sslinfo: add ssl_extension_info SRF

  11. Reduce ProcArrayLock contention by removing backends in batches.

  12. Fix `make installcheck` for serializable transactions.

  13. Lockless StrategyGetBuffer clock sweep hot path.

  14. Reduce sinval synchronization overhead.