Horton

Re: Possible performance regression in version 10.1 with pgbench read-write tests.

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Mithun Cy <mithun.cy@enterprisedb.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Amit Kapila <amit.kapila16@gmail.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-07-20T19:35:39Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2018-07-21 00:53:28 +0530, Mithun Cy wrote:
>> I did a quick test applying the patch with same settings as initial mail I
>> have reported  (On postgresql 10 latest code)
>> 72 clients
>> 
>> CASE 1:
>> Without Patch : TPS 29269.823540
>> 
>> With Patch : TPS 36005.544960.    --- 23% jump
>> 
>> Just Disabling using unnamed POSIX semaphores: TPS 34481.207959

>> So it seems that is the issue as the test is being run on 8 node numa
>> machine.

> Cool. I think we should just backpatch that then.  Does anybody want to
> argue against?

Not entirely clear to me what change is being proposed here?

In any case, I strongly resist making performance-based changes on
the basis of one test on one kernel and one hardware platform.
We should reproduce the results on a few different machines before
we even think of committing anything.  I'm happy to test on what
I have, although I'd be the first to agree that what I'm checking
is relatively low-end cases.  (Too bad hydra's gone.)

			regards, tom lane

Commits

  1. Pad semaphores to avoid false sharing.