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Message-Id: <20070410014102.fd730911.akpm@linux-foundation.org>
Date: Tue, 10 Apr 2007 01:41:02 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jeff Garzik <jeff@...zik.org>
Cc: Dave Jones <davej@...hat.com>, Robin Holt <holt@....com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Ingo Molnar <mingo@...e.hu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Jack Steiner <steiner@...ricas.sgi.com>
Subject: Re: init's children list is long and slows reaping children.
On Tue, 10 Apr 2007 04:33:57 -0400 Jeff Garzik <jeff@...zik.org> wrote:
> Andrew Morton wrote:
> > On Tue, 10 Apr 2007 03:05:56 -0400 Jeff Garzik <jeff@...zik.org> wrote:
> >
> >> My main
> >> worry with keventd is that we might get stuck behind an unrelated
> >> process for an undefined length of time.
> >
> > I don't think it has ever been demonstrated that keventd latency is
> > excessive, or a problem. I guess we could instrument it and fix stuff
> > easily enough.
>
> It's simple math, combined with user expectations.
>
> On a 1-CPU or 2-CPU box, if you have three or more tasks, all of which
> are doing hardware reset tasks that could take 30-60 seconds (realistic
> for libata, SCSI and network drivers, at least), then OBVIOUSLY you have
> other tasks blocked for that length of time.
Well that obviously would be a dumb way to use keventd. One would need
to do schedule_work(), kick off the reset then do schedule_delayed_work()
to wait (or poll) for its termination.
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