freebsd-performance Digest, Vol 69, Issue 2

[Sam Xia]

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 at freebsd.org 
> [mailto:owner-freebsd-performance at 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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> Today's Topics:
> 
>    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 at bulinfo.net>
> Subject: Re: 1. thread switching time? (Krassimir Slavchev)
> To: Julian Elischer <julian at elischer.org>
> Cc: freebsd-performance at freebsd.org, Sam Xia <xiazhongqi at huawei.com>
> Message-ID: <490EDD49.5070902 at 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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