Horton

Re: Speed up Clog Access by increasing CLOG buffers

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Robert Haas <robertmhaas@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: 2016-10-21T02:44:05Z
Lists: pgsql-hackers 
On Thu, Oct 20, 2016 at 9:15 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> So here's my theory.  The whole reason why Tomas is having difficulty
> seeing any big effect from these patches is because he's testing on
> x86.  When Dilip tests on x86, he doesn't see a big effect either,
> regardless of workload.  But when Dilip tests on POWER, which I think
> is where he's mostly been testing, he sees a huge effect, because for
> some reason POWER has major problems with this lock that don't exist
> on x86.

Right, because on POWER we can see big contention on ClogControlLock
with 300 scale factor, even at 96 client count, but on X86 with 300
scan factor there is almost no contention on ClogControlLock.

However at 1000 scale factor we can see significant contention on
ClogControlLock on X86 machine.

I want to test on POWER with 1000 scale factor to see whether
contention on ClogControlLock become much worse ?

I will run this test and post the results.

-- 
Regards,
Dilip Kumar
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.