Horton

Re: Speed up Clog Access by increasing CLOG buffers

Jim Nasby <jim.nasby@bluetreble.com>

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From: Jim Nasby <Jim.Nasby@BlueTreble.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-10-31T04:01:52Z
Lists: pgsql-hackers 
On 10/30/16 1:32 PM, Tomas Vondra wrote:
>
> Now, maybe this has nothing to do with PostgreSQL itself, but maybe it's
> some sort of CPU / OS scheduling artifact. For example, the system has
> 36 physical cores, 72 virtual ones (thanks to HT). I find it strange
> that the "good" client counts are always multiples of 72, while the
> "bad" ones fall in between.
>
>   72 = 72 * 1   (good)
>  108 = 72 * 1.5 (bad)
>  144 = 72 * 2   (good)
>  180 = 72 * 2.5 (bad)
>  216 = 72 * 3   (good)
>  252 = 72 * 3.5 (bad)
>  288 = 72 * 4   (good)
>
> So maybe this has something to do with how OS schedules the tasks, or
> maybe some internal heuristics in the CPU, or something like that.

It might be enlightening to run a series of tests that are 72*.1 or *.2 
apart (say, 72, 79, 86, ..., 137, 144).
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)   mobile: 512-569-9461

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.