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linux-aio: track whether the queue is blocked 

Avoid that unplug submits requests when io_submit reported that it
couldn't accept more; at the same time, try more io_submit calls if it
could handle the whole set of requests that were passed, so that the
"blocked" flag is reset as soon as possible.

After the previous patch, laio_submit already tried to avoid submitting
requests to a blocked queue, by comparing s->io_q.idx with "==" instead
of the more natural ">=".  Switch to the simpler expression now that we
have the "blocked" flag.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-11 14:52:27 +01:00 committed by Stefan Hajnoczi
parent 28b240877b
commit 43f2376e09
1 changed files with 27 additions and 20 deletions
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47
block/linux-aio.c
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@ -41,6 +41,7 @@ struct qemu_laiocb {
typedef struct {
int plugged;
unsigned int idx;
bool blocked;
QSIMPLEQ_HEAD(, qemu_laiocb) pending;
} LaioQueue;
@ -180,34 +181,39 @@ static void ioq_init(LaioQueue *io_q)
QSIMPLEQ_INIT(&io_q->pending);
io_q->plugged = 0;
io_q->idx = 0;
io_q->blocked = false;
}
static int ioq_submit(struct qemu_laio_state *s)
{
int ret, i;
int len = 0;
int ret, i, len;
struct qemu_laiocb *aiocb;
struct iocb *iocbs[MAX_QUEUED_IO];
QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) {
iocbs[len++] = &aiocb->iocb;
if (len == MAX_QUEUED_IO) {
break;
do {
len = 0;
QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) {
iocbs[len++] = &aiocb->iocb;
if (len == MAX_QUEUED_IO) {
break;
}
}
}
ret = io_submit(s->ctx, len, iocbs);
if (ret == -EAGAIN) {
ret = 0;
}
if (ret < 0) {
abort();
}
ret = io_submit(s->ctx, len, iocbs);
if (ret == -EAGAIN) {
ret = 0;
}
if (ret < 0) {
abort();
}
for (i = 0; i < ret; i++) {
s->io_q.idx--;
QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
}
} while (ret == len && !QSIMPLEQ_EMPTY(&s->io_q.pending));
s->io_q.blocked = (s->io_q.idx > 0);
for (i = 0; i < ret; i++) {
s->io_q.idx--;
QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
}
return ret;
}
@ -229,7 +235,7 @@ int laio_io_unplug(BlockDriverState *bs, void *aio_ctx, bool unplug)
return 0;
}
if (!QSIMPLEQ_EMPTY(&s->io_q.pending)) {
if (!s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
ret = ioq_submit(s);
}
@ -271,7 +277,8 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
QSIMPLEQ_INSERT_TAIL(&s->io_q.pending, laiocb, next);
s->io_q.idx++;
if (s->io_q.idx == (s->io_q.plugged ? MAX_QUEUED_IO : 1)) {
if (!s->io_q.blocked &&
(!s->io_q.plugged || s->io_q.idx >= MAX_QUEUED_IO)) {
ioq_submit(s);
}
return &laiocb->common;