| From: | Matteo Beccati <php(at)beccati(dot)com> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Mateusz Guzik <mjguzik(at)gmail(dot)com>, Keith Fiske <keith(at)omniti(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Marko Tiikkaja <marko(at)joh(dot)to>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Noah Misch <noah(at)leadboat(dot)com> |
| Subject: | Re: [HACKERS] kqueue |
| Date: | 2018-10-01 17:25:45 |
| Message-ID: | fa1efd20-60a3-90ef-7b75-1c7d5cd28d03@beccati.com |
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| Lists: | pgsql-hackers |
Hi Thomas,
On 01/10/2018 01:09, Thomas Munro wrote:
> I don't know why the existence of the kqueue should make recvfrom()
> slower on the pgbench side. That's probably something to look into
> off-line with some FreeBSD guru help. Degraded performance for
> clients on the same machine does seem to be a show stopper for this
> patch for now. Thanks for testing!
Glad to be helpful!
I've tried running pgbench from a separate VM and in fact kqueue
consistently takes the lead with 5-10% more tps on select/prepared
pgbench on NetBSD too.
What I have observed is that sys cpu usage is ~65% (35% idle) with
kqueue, while unpatched master averages at 55% (45% idle): relatively
speaking that's almost 25% less idle cpu available for a local pgbench
to do its own stuff.
Running pgbench locally shows an average 47% usr / 53% sys cpu
distribution w/ kqueue vs more like 50-50 w/ vanilla, so I'm inclined to
think that's the reason why we see a performance drop instead. Thoguhts?
Cheers
--
Matteo Beccati
Development & Consulting - http://www.beccati.com/
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