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: Robert Haas <robertmhaas@gmail.com>
Cc: 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: 2016-11-04T09:20:06Z
Lists: pgsql-hackers 
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.

-- 
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.