From: Arjan van de Ven <arjan@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Robert Swan <swan.r.l@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
linux-kernel@vger.kernel.org
Subject: Re: [bisected] pty performance problem
Date: Sat, 21 Nov 2009 23:15:14 -0800 [thread overview]
Message-ID: <20091121231514.3012e679@infradead.org> (raw)
In-Reply-To: <20091122063926.GA18224@elte.hu>
On Sun, 22 Nov 2009 07:39:26 +0100
Ingo Molnar <mingo@elte.hu> wrote:
> > ! Neither has any I/O apart from the pty conversation, so I'd
> > expect to ! see CPU usage at 100%. When I ran it, the CPU was
> > pretty well idle. ! After a fair bit of fiddling, it turned out
> > that both sides were ! taking about 8ms for their read() calls. At
> > that point it seemed ! pretty clear that this was a delay in the
> > kernel, not the code. !
> > [snip]
> >
> > I can provide reasonably stripped down code which demonstrates the
> > problem. It has been reproduced by one other person, though his
> > delay was about 2ms.
let me guess; you have HZ=250 and the other person has HZ=1000...
since this seems consistent with doing a 1 jiffy delay...
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2009-11-22 7:13 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-21 22:23 Robert Swan
2009-11-21 23:23 ` Alan Cox
2009-11-22 0:27 ` Robert Swan
2009-11-22 12:29 ` Alan Cox
2009-11-22 12:41 ` Mike Galbraith
2009-11-22 21:37 ` Robert Swan
2009-11-22 6:39 ` Ingo Molnar
2009-11-22 7:15 ` Arjan van de Ven [this message]
2009-11-22 21:56 ` Robert Swan
2009-11-22 12:23 ` Alan Cox
2009-11-22 12:42 ` Ingo Molnar
2009-11-23 5:00 ` Mike Galbraith
2009-11-23 10:28 ` Alan Cox
2009-11-23 11:31 ` Alan Cox
2009-11-23 11:48 ` Ingo Molnar
2009-11-23 11:59 ` Alan Cox
2009-11-23 12:04 ` Ingo Molnar
2009-11-23 13:34 ` Alan Cox
2009-11-23 17:48 ` Ingo Molnar
2011-07-09 6:29 ` Robert Swan
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