Date: Tue, 04 Nov 2008 11:05:06 +0800 From: Sam Xia <xiazhongqi@huawei.com> To: freebsd-performance@freebsd.org Cc: 'Krassimir Slavchev' <krassi@bulinfo.net> Subject: RE: freebsd-performance Digest, Vol 69, Issue 2 Message-ID: <000001c93e2a$23db4150$2f096f0a@china.huawei.com> In-Reply-To: <20081103120020.5188D106579C@hub.freebsd.org>
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if you modify file subr_param.c as follows:
void
init_param1(void)
{
hz = HZ; ===> hz=HZ*4
.
.
.
}
you will get what you want. i have tested.it works well.
Best Regards, Sam Xia
> -----Original Message-----
> From: owner-freebsd-performance@freebsd.org
> [mailto:owner-freebsd-performance@freebsd.org] On Behalf Of
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> Sent: Monday, November 03, 2008 8:00 PM
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> Subject: freebsd-performance Digest, Vol 69, Issue 2
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> 1. Re: 1. thread switching time? (Krassimir Slavchev)
> (Krassimir Slavchev)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 03 Nov 2008 13:15:21 +0200
> From: Krassimir Slavchev <krassi@bulinfo.net>
> Subject: Re: 1. thread switching time? (Krassimir Slavchev)
> To: Julian Elischer <julian@elischer.org>
> Cc: freebsd-performance@freebsd.org, Sam Xia <xiazhongqi@huawei.com>
> Message-ID: <490EDD49.5070902@bulinfo.net>
> Content-Type: text/plain; charset=ISO-8859-1
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> Julian Elischer wrote:
> > Krassimir Slavchev wrote:
> >
> >>
> >> Also, I am able to set HZ=100000 but the thread switching time is
> >> still ~1ms.
> >
> > You must be talking about the time that a thread can run
> before it is
> > pushed out by other threads? I know I've seem many x
> 10,000 context
> > switches in some cases, i.e. look at very high interrupt
> rates etc. so
> > I guess I'm not sure what you are measuring..
> >
> > at one time the scheduling quantum was independent of Hz.
> > I am not sure how true that is now..
> >
>
> The scheduling quantum is independent of Hz for Hz > 1000.
>
> usr/src/sys/kern_tc.c:
> ...
> if (hz > 1000)
> tc_tick = (hz + 500) / 1000;
> else
> tc_tick = 1;
> ...
>
> I am not sure whether setting Hz > 1000 impact on performance
> or not, e.g using polling(4).
> Removing this limitation and setting kern.hz=10000 give
> 100usec quantum.
>
> Thanks for the point.
>
> Best Regards
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