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Date: Wed, 20 Mar 2013 15:56:33 +0100
From: =?iso-8859-1?Q?Beno=EEt?= Canet <benoit.canet@irqsave.net>
Message-ID: <20130320145633.GA1473@irqsave.net>
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Subject: Re: [Qemu-devel] [PATCH] block: fix bdrv_exceed_iops_limits wait
 computation
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: kwolf@redhat.com, wuzhy@linux.vnet.ibm.com, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

> But I don't understand why bs->slice_time is modified instead of keepin=
g
> it constant at 100 ms:
>
>     bs->slice_time =3D wait_time * BLOCK_IO_SLICE_TIME * 10;
>     bs->slice_end +=3D bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
>     if (wait) {
>         *wait =3D wait_time * BLOCK_IO_SLICE_TIME * 10;
>     }

In bdrv_exceed_bps_limits there is an equivalent to this with a comment.

---------
  /* When the I/O rate at runtime exceeds the limits,
     * bs->slice_end need to be extended in order that the current statis=
tic
     * info can be kept until the timer fire, so it is increased and tune=
d
     * based on the result of experiment.
     */
    bs->slice_time =3D wait_time * BLOCK_IO_SLICE_TIME * 10;
    bs->slice_end +=3D bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
    if (wait) {
        *wait =3D wait_time * BLOCK_IO_SLICE_TIME * 10;
    }
----------

Yes I will try your patch.

Regards

Beno=EEt