Horton

Re: Speed up Clog Access by increasing CLOG buffers

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-10-12T18:55:26Z
Lists: pgsql-hackers 
On Wed, Oct 12, 2016 at 3:21 AM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> I think at higher client count from client count 96 onwards contention
> on CLogControlLock is clearly visible and which is completely solved
> with group lock patch.
>
> And at lower client count 32,64  contention on CLogControlLock is not
> significant hence we can not see any gain with group lock patch.
> (though we can see some contention on CLogControlLock is reduced at 64
> clients.)

I agree with these conclusions.  I had a chance to talk with Andres
this morning at Postgres Vision and based on that conversation I'd
like to suggest a couple of additional tests:

1. Repeat this test on x86.  In particular, I think you should test on
the EnterpriseDB server cthulhu, which is an 8-socket x86 server.

2. Repeat this test with a mixed read-write workload, like -b
tpcb-like@1 -b select-only@9

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.