From: Ingo Molnar <mingo@elte.hu>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: jdike@addtoit.com, user-mode-linux-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: scheduling anomaly on uml (was: -rt doesn't compile for UML)
Date: Thu, 29 Nov 2007 12:50:11 +0100 [thread overview]
Message-ID: <20071129115011.GA30208@elte.hu> (raw)
In-Reply-To: <E1Ixhgf-0001CF-MC@dorka.pomaz.szeredi.hu>
* Miklos Szeredi <miklos@szeredi.hu> wrote:
> > how come UML idled for 30 msecs here, while the workload was
> > supposed to be CPU-bound? It's not IO bound anywhere, right? No SMP
> > artifacts either, right?
>
> Yes. The UML kernel is UP, and I don't think 'date' or 'bash' want to
> do any disk I/O.
>
> Could disk I/O be blocking the tty? I think UML uses separate threads
> for these, but I don't know the details.
even if the workload is fully CPU bound externally - internally a
request to the external (CPU-bound) thread will look like an asynchonous
request - so small amounts of idle time can be within UML, legitimately.
(for the amount of time it takes for the external thread to service the
request)
30 msecs already sounds a bit excessive (this is on your T60 with
Core2Duo, right?), and 1-2 seconds noticeable latency is definitely
excessive.
Ingo
next prev parent reply other threads:[~2007-11-29 11:50 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-28 12:47 -rt doesn't compile for UML Miklos Szeredi
2007-11-28 12:50 ` Ingo Molnar
2007-11-28 13:09 ` Miklos Szeredi
2007-11-28 13:15 ` Ingo Molnar
2007-11-28 13:15 ` Ingo Molnar
2007-11-28 13:24 ` Miklos Szeredi
2007-11-28 15:08 ` Jeff Dike
2007-11-28 15:38 ` Miklos Szeredi
2007-11-28 15:41 ` Ingo Molnar
2007-11-28 16:00 ` Miklos Szeredi
2007-11-28 16:05 ` Ingo Molnar
2007-11-28 16:57 ` Miklos Szeredi
2007-11-28 17:02 ` Ingo Molnar
2007-11-28 17:02 ` Miklos Szeredi
2007-11-28 17:24 ` Ingo Molnar
2007-11-28 17:25 ` Miklos Szeredi
2007-11-28 17:38 ` Jeff Dike
2007-11-28 15:06 ` Jeff Dike
2007-11-28 15:35 ` Miklos Szeredi
2007-11-28 18:29 ` Jeff Dike
2007-11-28 18:37 ` Ingo Molnar
2007-11-28 18:46 ` Miklos Szeredi
2007-11-29 10:19 ` scheduling anomaly on uml (was: -rt doesn't compile for UML) Miklos Szeredi
2007-11-29 10:57 ` Ingo Molnar
2007-11-29 11:36 ` Miklos Szeredi
2007-11-29 11:50 ` Ingo Molnar [this message]
2007-11-29 16:07 ` Miklos Szeredi
2007-11-29 16:25 ` Ingo Molnar
2007-11-29 18:05 ` Miklos Szeredi
2007-11-29 19:26 ` Ingo Molnar
2007-11-29 17:02 ` Jeff Dike
2007-11-29 17:16 ` Ingo Molnar
2007-11-29 17:58 ` Miklos Szeredi
2007-11-30 19:44 ` Miklos Szeredi
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