Horton

Re: Fix performance of generic atomics

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Sokolov Yura <funny.falcon@postgrespro.ru>
Cc: Simon Riggs <simon@2ndquadrant.com>, Jeff Janes <jeff.janes@gmail.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, pgsql-hackers-owner@postgresql.org
Date: 2017-09-06T13:36:36Z
Lists: pgsql-hackers 
Sokolov Yura <funny.falcon@postgrespro.ru> writes:
> On 2017-09-06 15:56, Tom Lane wrote:
>> The point I'm trying to make is that if tweaking generic.h improves
>> performance then it's an indicator of missed cases in the less-generic
>> atomics code, and the latter is where our attention should be focused.
>> I think basically all of the improvement Sokolov got was from upgrading
>> the coverage of generic-gcc.h.

> Not exactly. I've checked, that new version of generic 
> pg_atomic_fetch_or_u32
> loop also gives improvement.

But once you put in the generic-gcc version, that's not reached anymore.

			regards, tom lane

Commits

  1. Further marginal hacking on generic atomic ops.

  2. Use more of gcc's __sync_fetch_and_xxx builtin functions for atomic ops.

  3. Remove duplicate reads from the inner loops in generic atomic ops.