Subject: Re: what to revert
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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <c7ad0f06-52c6-6284-c3a0-251807be9d3f@2ndquadrant.com>
Date: Tue, 3 May 2016 20:57:13 +0200
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On 05/03/2016 07:41 PM, Andres Freund wrote:
> On 2016-05-03 11:46:23 -0500, Kevin Grittner wrote:
>>> was immediately addressed by another round of benchmarks after you
>>> pointed it out.
>>
>> Which showed a 4% maximum hit before moving the test for whether it
>> was "off" inline.
>
>> (I'm not clear from the posted results whether that was before or
>> after skipping the spinlock when the feature was off.)
>
> They're from after the spinlock issue was resolved. Before that the
> issue was a lot worse (see mail linked two messages upthread).
>
>
> I'm pretty sure that I said that somewhere else at least once: But to
> be absolutely clear, I'm *not* really concerned with the performance
> with the feature turned off. I'm concerned about the performance with
> it turned on.

If you tell me how to best test it, I do have a 4-socket server sitting 
idly in the corner (well, a corner reachable by SSH). I can get us some 
numbers, but I haven't been following the snapshot_too_old so I'll need 
some guidance on what to test.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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