Re: Speed up Clog Access by increasing CLOG buffers

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Speed up Clog Access by increasing CLOG buffers
Date: 2017-03-09 22:49:42
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On Tue, Jan 31, 2017 at 11:35 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
>> Thanks for the review.
> Moved to CF 2017-03, the 8th commit fest of this patch.

I think eight is enough. Committed with some cosmetic changes.

I think the turning point for this somewhat-troubled patch was when we
realized that, while results were somewhat mixed on whether it
improved performance, wait event monitoring showed that it definitely
reduced contention significantly. However, I just realized that in
both this case and in the case of group XID clearing, we weren't
advertising a wait event for the PGSemaphoreLock calls that are part
of the group locking machinery. I think we should fix that, because a
quick test shows that can happen fairly often -- not, I think, as
often as we would have seen LWLock waits without these patches, but
often enough that you'll want to know. Patch attached.

Robert Haas
The Enterprise PostgreSQL Company

Attachment Content-Type Size
group-update-waits-v1.patch application/octet-stream 4.8 KB

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