Re: [HACKERS] Speed up Clog Access by increasing CLOG buffers

On Tue, Jan 31, 2017 at 11:35 PM, Michael Paquier
<michael.paquier@gmail.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
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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