Date: Wed, 3 Mar 2004 16:50:22 +0300 From: Sergey 'DoubleF' Zaharchenko <doublef@tele-kom.ru> To: zhangweiwu@realss.com Cc: questions@freebsd.org Subject: Re: priority-- curious about cpu resouce share Message-ID: <20040303165022.49f2fac9@Hal.localdomain> In-Reply-To: <Law11-F539uwETDgZbo0001f813@hotmail.com> References: <Law11-F539uwETDgZbo0001f813@hotmail.com>
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On Wed, 03 Mar 2004 00:34:37 +0800
"Zhang Weiwu" <weiwuzhang@hotmail.com> probably wrote:
> Today I did't experiment on {rt|id}prio(1), just to be interesting. I am
> trying to understand FreeBSD priority mechenism. IMHO realtime/idle
> priority only starvs processes when there is no cpu resource at all.
>
> To test, I run mpg321 on realtime priority 3, run ppp on realtime priority
> 4, a little lower than mpg321, and scp over the ppp tunnel on normal
> priority.
>
> Top(1) shows an average about:
> 55.2% user, 0.0% nice, 21.5% system, 12.2% interrupt, 11.1% idle
> * mpg321 takes average about 70%;
> * ppp is seriously slowed down, it takes about 1.5% (normally 17% on full
> speed);
> * sshd almost starves; it takes 0.00% (normally 2%) and only transfer
> several bytes once several minutes; the otherside scp prompts "stalled".
sshd doesn't starve CPU, I guess; as you reach it through ppp, and ppp
gets slow, sshd does, too.
> I'm the kind of newbie think 11.1% idle cpu time to be free cpu resource,
> because I don't have idle process. I wish to know why, as there are still
> 11.1% free cpu resource, ppp and sshd doesn't get this share?
The most frequent cause is that they don't need the CPU so much as
something else, like disk I/O, etc. Could you please post the whole
output of top (and a snapshot of systat -vmstat, for example)?
> Just to be curious. Thank you.
FWIW, splay uses <30% of a P150:)
--
DoubleF
A jury consists of 12 persons chosen to decide
who has the better lawyer.
-- Robert Frost
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