Date: Mon, 9 May 2005 14:22:36 -0400 From: Suleiman Souhlal <ssouhlal@FreeBSD.org> To: Pete French <petefrench@ticketswitch.com> Cc: freebsd-stable@FreeBSD.org Subject: Re: Performance issue Message-ID: <2B4490FF-FEFD-473F-BDF0-293C468A55B9@FreeBSD.org> In-Reply-To: <E1DVC6B-000FgV-9j@dilbert.firstcallgroup.co.uk> References: <E1DVC6B-000FgV-9j@dilbert.firstcallgroup.co.uk>
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Hello,
On May 9, 2005, at 1:31 PM, Pete French wrote:
>> 5.3 ships with SMP turned on, which makes lock operations rather
>> expensive on single-processor machines. 4.x does not have SMP
>> turned on by default. Would you be able to re-run your test with
>> SMP turned off?
>>
>
> I just ran a test here with SMP turned of on 5.4-RC4 (GENERIC) I
> got the
> following result:
>
> 67.52 real 41.13 user 26.16 sys
> 7034 involuntary context switches
>
> i.e. it still has system time a a huge proportion of the total
> compared
> to the 4.11 kernel. Interesingly, after reading Holger Kipp's results
> I tried it on a genuine multi-processor box with SMP enabled
> running 5.3.
> He got a very small percentage of the time in sys (3.51 out of
> 81.90) but
> I got:
> 255.30 real 160.20 user 88.50 sys
>
> Once again a far higher proprtion of the time spent in sys than you
> would
> expect.
I ran ktrace(1) on it, and it appears that python keeps calling
sigprocmask() continually:
673 python 0.000007 CALL sigprocmask(0x3,0,0x811d11c)
673 python 0.000005 RET sigprocmask 0
673 python 0.000009 CALL sigprocmask(0x1,0,0x8113d1c)
673 python 0.000005 RET sigprocmask 0
etc..
This explains why it's using so much system time. Now the question is
why is python doing this?
--
Suleiman Souhlal | ssouhlal@vt.edu
The FreeBSD Project | ssouhlal@FreeBSD.org
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