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Re: [Qemu-devel] [PATCH v3 1/3] linux-aio: fix submit aio as a batch
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/3] linux-aio: fix submit aio as a batch |
Date: |
Tue, 18 Nov 2014 15:18:57 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
> @@ -137,6 +145,12 @@ static void qemu_laio_completion_bh(void *opaque)
> }
> }
>
> +static void qemu_laio_start_retry(struct qemu_laio_state *s)
> +{
> + if (s->io_q.idx)
> + qemu_bh_schedule(s->io_q.retry);
> +}
> +
> static void qemu_laio_completion_cb(EventNotifier *e)
> {
> struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
> @@ -144,6 +158,7 @@ static void qemu_laio_completion_cb(EventNotifier *e)
> if (event_notifier_test_and_clear(&s->e)) {
> qemu_bh_schedule(s->completion_bh);
> }
> + qemu_laio_start_retry(s);
I think you do not even need two bottom halves. Just call ioq_submit
from completion_bh instead, after the call to io_getevents.
> }
>
> static void laio_cancel(BlockAIOCB *blockacb)
> @@ -163,6 +178,9 @@ static void laio_cancel(BlockAIOCB *blockacb)
> }
>
> laiocb->common.cb(laiocb->common.opaque, laiocb->ret);
> +
> + /* check if there are requests in io queue */
> + qemu_laio_start_retry(laiocb->ctx);
> }
>
> static const AIOCBInfo laio_aiocb_info = {
> @@ -177,45 +195,80 @@ static void ioq_init(LaioQueue *io_q)
> io_q->plugged = 0;
> }
>
> -static int ioq_submit(struct qemu_laio_state *s)
> +static void abort_queue(struct qemu_laio_state *s)
> +{
> + int i;
> + for (i = 0; i < s->io_q.idx; i++) {
> + struct qemu_laiocb *laiocb = container_of(s->io_q.iocbs[i],
> + struct qemu_laiocb,
> + iocb);
> + laiocb->ret = -EIO;
> + qemu_laio_process_completion(s, laiocb);
> + }
> +}
> +
> +static int ioq_submit(struct qemu_laio_state *s, bool enqueue)
> {
> int ret, i = 0;
> int len = s->io_q.idx;
> + int j = 0;
>
> - do {
> - ret = io_submit(s->ctx, len, s->io_q.iocbs);
> - } while (i++ < 3 && ret == -EAGAIN);
> + if (!len) {
> + return 0;
> + }
>
> - /* empty io queue */
> - s->io_q.idx = 0;
> + ret = io_submit(s->ctx, len, s->io_q.iocbs);
> + if (ret == -EAGAIN) { /* retry in following completion cb */
> + return 0;
> + } else if (ret < 0) {
> + if (enqueue) {
> + return ret;
> + }
>
> - if (ret < 0) {
> - i = 0;
> - } else {
> - i = ret;
> + /* in non-queue path, all IOs have to be completed */
> + abort_queue(s);
> + ret = len;
> + } else if (ret == 0) {
> + goto out;
No need for goto; just move the "for" loop inside this conditional. Or
better, just use memmove. That is:
if (ret < 0) {
if (ret == -EAGAIN) {
return 0;
}
if (enqueue) {
return ret;
}
abort_queue(s);
ret = len;
}
if (ret > 0) {
memmove(...)
s->io_q.idx -= ret;
}
return ret;
> + * update io queue, for partial completion, retry will be
> + * started automatically in following completion cb.
> + */
> + s->io_q.idx -= ret;
> +
> return ret;
> }
>
> -static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
> +static void ioq_submit_retry(void *opaque)
> +{
> + struct qemu_laio_state *s = opaque;
> + ioq_submit(s, false);
> +}
> +
> +static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
> {
> unsigned int idx = s->io_q.idx;
>
> + if (unlikely(idx == s->io_q.size)) {
> + return -1;
return -EAGAIN?
Thanks,
Paolo
> + }
> +
> s->io_q.iocbs[idx++] = iocb;
> s->io_q.idx = idx;
>
> - /* submit immediately if queue is full */
> - if (idx == s->io_q.size) {
> - ioq_submit(s);
> + /* submit immediately if queue depth is above 2/3 */
> + if (idx > s->io_q.size * 2 / 3) {
> + return ioq_submit(s, true);
> }
> +
> + return 0;
> }
>
> void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
> @@ -237,7 +290,7 @@ int laio_io_unplug(BlockDriverState *bs, void *aio_ctx,
> bool unplug)
> }
>
> if (s->io_q.idx > 0) {
> - ret = ioq_submit(s);
> + ret = ioq_submit(s, false);
> }
>
> return ret;
> @@ -281,7 +334,9 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void
> *aio_ctx, int fd,
> goto out_free_aiocb;
> }
> } else {
> - ioq_enqueue(s, iocbs);
> + if (ioq_enqueue(s, iocbs) < 0) {
> + goto out_free_aiocb;
> + }
> }
> return &laiocb->common;
>
> @@ -296,12 +351,14 @@ void laio_detach_aio_context(void *s_, AioContext
> *old_context)
>
> aio_set_event_notifier(old_context, &s->e, NULL);
> qemu_bh_delete(s->completion_bh);
> + qemu_bh_delete(s->io_q.retry);
> }
>
> void laio_attach_aio_context(void *s_, AioContext *new_context)
> {
> struct qemu_laio_state *s = s_;
>
> + s->io_q.retry = aio_bh_new(new_context, ioq_submit_retry, s);
> s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s);
> aio_set_event_notifier(new_context, &s->e, qemu_laio_completion_cb);
> }
>
[Qemu-devel] [PATCH v3 2/3] linux-aio: handling -EAGAIN for !s->io_q.plugged case, Ming Lei, 2014/11/06