Date: Tue, 20 Nov 2007 20:37:57 +0300 From: Alexey Popov <lol@chistydom.ru> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-stable@freebsd.org Subject: Re: 2 x quad-core system is slower that 2 x dual core on FreeBSD Message-ID: <47431B75.4040601@chistydom.ru> In-Reply-To: <9bbcef730711200915n12e37efcs67cf260641b9baab@mail.gmail.com> References: <4741905E.8050300@chistydom.ru> <fhs3s5$knj$1@ger.gmane.org> <47419AB3.5030008@chistydom.ru> <fhs7db$2es$1@ger.gmane.org> <4741B3DE.2000009@chistydom.ru> <fhsl0v$n85$1@ger.gmane.org> <47430AE8.7050408@chistydom.ru> <9bbcef730711200915n12e37efcs67cf260641b9baab@mail.gmail.com>
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Hi.
Ivan Voras wrote:
>> CPU states: 5.9% user, 0.0% nice, 81.3% system, 0.0% interrupt, 12.8% idle
>> CPU states: 82.2% user, 0.0% nice, 13.8% system, 0.0% interrupt, 4.0% idle
> Interesting coincidence: 1 CPU generates almost 8x less "sys time" then 8 CPUs.
> But it seems that you have found something real. Inspired by your
> problem I've done a simple measurement ("ab") on a 4-CPU (2x2 core
> Opterons 2216 HE, PAE) machine I maintain, under these circumstances:
>
> - a "heavy" PHP application
> - FastCGI
> - in this case, load of 4 clients
> - on 6-STABLE
>
> and I'm reporting similar findings:
> CPU states: 38.8% user, 0.0% nice, 48.4% system, 3.2% interrupt, 9.6% idle
> We are not so performance bound as you so I didn't do measurements
> earlier. I cannot "play" with settings on this machine as it is in
> production, but ~~50% sys time (the measurement changes around 45% +/-
> 10%) seems too much.
Thank you for your research. I think you can get more %sys with 4-core
processors. For me 2xquad-core systems are now completely unusable as
PHP backends.
Anyway I'm happy that I'm not alone with this problem. But what can we
do about it?
With best regards,
Alexey Popov
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