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Date:      Fri, 23 Nov 2007 11:57:35 +0100
From:      Kris Kennaway <kris@FreeBSD.org>
To:        Alexey Popov <lol@chistydom.ru>
Cc:        Attilio Rao <attilio@freebsd.org>, freebsd-stable@freebsd.org
Subject:   Re: 2 x quad-core system is slower that 2 x dual core on FreeBSD
Message-ID:  <4746B21F.7050906@FreeBSD.org>
In-Reply-To: <47468165.5010906@chistydom.ru>
References:  <4741905E.8050300@chistydom.ru>	<fhs3s5$knj$1@ger.gmane.org>	<47419AB3.5030008@chistydom.ru>	<fhs7hp$2es$2@ger.gmane.org> <4741A7DA.2050706@chistydom.ru> <4741DA15.9000308@FreeBSD.org> <47429DB8.7040504@chistydom.ru> <4742ADFE.40902@FreeBSD.org> <4742C46A.1060701@chistydom.ru> <47432F77.3030606@FreeBSD.org> <474339E9.4080301@FreeBSD.org> <4743629B.9090408@FreeBSD.org> <47456B71.5040205@chistydom.ru> <4745E5B3.6060200@FreeBSD.org> <47468165.5010906@chistydom.ru>

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Alexey Popov wrote:
> Hi.
> 
> Kris Kennaway wrote:
> 
>>> Now FreeBSD 7-STABLE ULE 8-core server without optimized PHP 
>>> realpath_cache_size (producing 2000+ lstats per request) can handle 
>>> up to ~24 rps as opposed to  max. 17 rps without your patch. %sys 
>>> never grows over %user with your patch. On the server with optimized 
>>> realpath_cache_size there's no visible influence of your patch.
>>
>> You said "20" before for this configuration, so I'm a bit suspicious 
>> about how seriously to treat your measurements :)
> Sorry, my mistake. s/ULE/4BSD.

OK, please compare ULE to ULE with and without my patch (and remembering 
to enable the sysctl), and obtain lock profiling traces in both cases 
under identical workloads & durations.  That is what I need to proceed 
with this issue.

>> Anyway, please obtain another lock profiling trace using the same 
>> conditions as the previous one (same workload & duration, etc), so we 
>> can compare what changed.
> OK, I'll make it a little bit later.
> 
> Also I tried to find what else is slow in FreeBSD, I tried hwpmc as 
> module and in kernel, but it fails with error:
> pmc: Unknown Intel CPU.
> module_register_init: MOD_LOAD (hwpmc, 0xffffffff804833e0, 
> 0xffffffff809338a0) error 78

There are patches you need to enable it on woodcrest.  They are in my p4 
branch (kris-contention) but I don't have time right now to extract them.

> This is related to 
> http://www.freebsd.org/cgi/query-pr.cgi?pr=amd64%2F111994&cat=
> and it is impossible to use hwpmc with modern CPUs.

Sounds like it.

> Is kgmon profiling usable on FreeBSD 7?

I've never bothered, it is likely to be quite slow, so it can totally 
change the workload you are trying to profile.

Kris



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