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