| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: heads up: Fix for intel hardware bug will lead to performance regressions |
| Date: | 2018-01-08 07:33:31 |
| Message-ID: | 20180108073330.sdv3r4k2rcn7xhip@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2018-01-08 14:38:20 +1300, Thomas Munro wrote:
> Just an idea, not sure if it's worth looking into; maybe we already
> spend enough time filling those buffers that a 50% syscall markup
> won't hurt.
Yea, I suspect that won't make a huge difference - copying an 8kb buffer
is typically a lot more than the overhead. The big problem for the
demonstrated slowness is really that we send a lot of tiny packets back
and forth and wait for them, and that's obviously going to be
performance sensitive to syscall speed. Pipelining helps a lot, but
isn't that generally applicable... TBH, I don't really see that much we
can do from our side for readonly OLTP with prepared statements.
Greetings,
Andres Freund
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