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linux-aio: queue requests that cannot be submitted 

Keep a queue of requests that were not submitted; pass them to
the kernel when a completion is reported, unless the queue is
plugged.

The array of iocbs is rebuilt every time from scratch.  This
avoids keeping the iocbs array and list synchronized.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-2-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-11 14:52:26 +01:00 committed by Stefan Hajnoczi
parent b5cf2c1b08
commit 28b240877b
1 changed files with 34 additions and 43 deletions
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77
block/linux-aio.c
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@ -35,14 +35,13 @@ struct qemu_laiocb {
size_t nbytes;
QEMUIOVector *qiov;
bool is_read;
QLIST_ENTRY(qemu_laiocb) node;
QSIMPLEQ_ENTRY(qemu_laiocb) next;
};
typedef struct {
struct iocb *iocbs[MAX_QUEUED_IO];
int plugged;
unsigned int size;
unsigned int idx;
QSIMPLEQ_HEAD(, qemu_laiocb) pending;
} LaioQueue;
struct qemu_laio_state {
@ -59,6 +58,8 @@ struct qemu_laio_state {
int event_max;
};
static int ioq_submit(struct qemu_laio_state *s);
static inline ssize_t io_event_ret(struct io_event *ev)
{
return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
@ -135,6 +136,10 @@ static void qemu_laio_completion_bh(void *opaque)
qemu_laio_process_completion(s, laiocb);
}
if (!s->io_q.plugged && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
ioq_submit(s);
}
}
static void qemu_laio_completion_cb(EventNotifier *e)
@ -172,52 +177,40 @@ static const AIOCBInfo laio_aiocb_info = {
static void ioq_init(LaioQueue *io_q)
{
io_q->size = MAX_QUEUED_IO;
io_q->idx = 0;
QSIMPLEQ_INIT(&io_q->pending);
io_q->plugged = 0;
io_q->idx = 0;
}
static int ioq_submit(struct qemu_laio_state *s)
{
int ret, i = 0;
int len = s->io_q.idx;
int ret, i;
int len = 0;
struct qemu_laiocb *aiocb;
struct iocb *iocbs[MAX_QUEUED_IO];
do {
ret = io_submit(s->ctx, len, s->io_q.iocbs);
} while (i++ < 3 && ret == -EAGAIN);
/* empty io queue */
s->io_q.idx = 0;
if (ret < 0) {
i = 0;
} else {
i = ret;
QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) {
iocbs[len++] = &aiocb->iocb;
if (len == MAX_QUEUED_IO) {
break;
}
}
for (; i < len; i++) {
struct qemu_laiocb *laiocb =
container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb);
ret = io_submit(s->ctx, len, iocbs);
if (ret == -EAGAIN) {
ret = 0;
}
if (ret < 0) {
abort();
}
laiocb->ret = (ret < 0) ? ret : -EIO;
qemu_laio_process_completion(s, laiocb);
for (i = 0; i < ret; i++) {
s->io_q.idx--;
QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
}
return ret;
}
static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
{
unsigned int idx = s->io_q.idx;
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);
}
}
void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
{
struct qemu_laio_state *s = aio_ctx;
@ -236,7 +229,7 @@ int laio_io_unplug(BlockDriverState *bs, void *aio_ctx, bool unplug)
return 0;
}
if (s->io_q.idx > 0) {
if (!QSIMPLEQ_EMPTY(&s->io_q.pending)) {
ret = ioq_submit(s);
}
@ -276,12 +269,10 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
}
io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
if (!s->io_q.plugged) {
if (io_submit(s->ctx, 1, &iocbs) < 0) {
goto out_free_aiocb;
}
} else {
ioq_enqueue(s, iocbs);
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)) {
ioq_submit(s);
}
return &laiocb->common;