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Message-ID: <6101e8c40805010814rf64d402l1a9da0c3e22b9668@mail.gmail.com>
Date: Thu, 1 May 2008 17:14:17 +0200
From: "Oliver Pinter" <oliver.pntr@gmail.com>
To: "Jeff Moyer" <jmoyer@redhat.com>
Subject: Re: [OP] v2.6.22.22-op1
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <x49fxt2axns.fsf@segfault.boston.devel.redhat.com>
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References: <db9953cd52eb63e471f5fcdcb83b299b@zipernowsky.hu>
	 <x49fxt2axns.fsf@segfault.boston.devel.redhat.com>
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On 5/1/08, Jeff Moyer <jmoyer@redhat.com> wrote:
> <oliver@zipernowsky.hu> writes:
>
> > I announced the v2.6.22.22-op1 "stable" kernel.
>
> >  fs/aio.c                    |   23 ++++++++++++-----------
>
> > Jeff Moyer (1):
> >       aio: account I/O wait time properly
>
> This version of the patch introduced a regression for UML.  It was
> seeing 100% iowait time when it wasn't waiting on any I/O.  There was a
> follow-up patch which did the io_schedule conditionally, see commit id:
>
>   e00ba3dae077f54cfd2af42e939a618caa7a3bca
>
> Cheers,
>
> Jeff
>
> > diff --git a/fs/aio.c b/fs/aio.c
> > index dbe699e..b3419c5 100644
> > --- a/fs/aio.c
> > +++ b/fs/aio.c
> > @@ -1170,7 +1171,7 @@ retry:
> >  			ret = 0;
> >  			if (to.timed_out)	/* Only check after read evt */
> >  				break;
> > -			schedule();
> > +			io_schedule();
> >  			if (signal_pending(tsk)) {
> >  				ret = -EINTR;
> >  				break;
>


hmm, this is the relevant code in 2.6.22:
----8<-------------->8-----
                        if (min_nr <= i)
                                break;
                        ret = 0;
                        if (to.timed_out)       /* Only check after read evt */
                                break;
                        schedule(); <-----------
                        if (signal_pending(tsk)) {
                                ret = -EINTR;
                                break;
                        }
                        /*ret = aio_read_evt(ctx, &ent);*/
----8<-------------->8-----

-- 
Thanks,
Oliver