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Re: Re: [Qemu-devel] [PATCH] qemu_aio_poll optimize
From: |
Wei Kong |
Subject: |
Re: Re: [Qemu-devel] [PATCH] qemu_aio_poll optimize |
Date: |
Mon, 15 Sep 2008 02:16:40 -0600 |
I will test the latest QEMU later.
--Best Regards
Kong Wei
>>> Anthony Liguori <address@hidden> 08/09/12 21:58 >>>
> qemu_aio_poll() exhaust 50% cpu utilization rate in whole qemu running,
> due to it scan RawAIOCB chain list loop and loop, especially when
> these RawAIOCB are still in EINPROGRESS at IO flood.
>
Have you tested this with the very latest QEMU SVN? The recent change
(yesterday) makes it so that qemu_aio_poll is not called in every CPU
iteration.
Regards,
Anthony Liguori
> This tune will reduce 2.2% ~ 2.5% total cpu utilization rate,
> qemu_aio_poll() will exhaust 5% cpu in whole qemu running
> and a little increase the IO through.
>
> Signed-off-by: Wei Kong <address@hidden>
> ---
>
> --- a/block-raw-posix.c
> +++ b/block-raw-posix.c
> @@ -289,40 +289,36 @@ void qemu_aio_poll(void)
> RawAIOCB *acb, **pacb;
> int ret;
>
> + pacb = &first_aio;
> for(;;) {
> - pacb = &first_aio;
> - for(;;) {
> - acb = *pacb;
> - if (!acb)
> - goto the_end;
> - ret = aio_error(&acb->aiocb);
> - if (ret == ECANCELED) {
> - /* remove the request */
> - *pacb = acb->next;
> - qemu_aio_release(acb);
> - } else if (ret != EINPROGRESS) {
> - /* end of aio */
> - if (ret == 0) {
> - ret = aio_return(&acb->aiocb);
> - if (ret == acb->aiocb.aio_nbytes)
> - ret = 0;
> - else
> - ret = -EINVAL;
> - } else {
> - ret = -ret;
> - }
> - /* remove the request */
> - *pacb = acb->next;
> - /* call the callback */
> - acb->common.cb(acb->common.opaque, ret);
> - qemu_aio_release(acb);
> - break;
> + acb = *pacb;
> + if (!acb)
> + break;
> + ret = aio_error(&acb->aiocb);
> + if (ret == EINPROGRESS) {
> + break;
> + } else if (ret != ECANCELED) {
> + /* end of aio */
> + if (ret == 0) {
> + ret = aio_return(&acb->aiocb);
> + if (ret == acb->aiocb.aio_nbytes)
> + ret = 0;
> + else
> + ret = -EINVAL;
> } else {
> - pacb = &acb->next;
> + ret = -ret;
> }
> - }
> + /* remove the request */
> + *pacb = acb->next;
> + /* call the callback */
> + acb->common.cb(acb->common.opaque, ret);
> + qemu_aio_release(acb);
> + } else {
> + /* remove the request */
> + *pacb = acb->next;
> + qemu_aio_release(acb);
> + }
> }
> - the_end: ;
> }
>
> /* Wait for all IO requests to complete. */
>
>
>