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linux-aio: add `dev_max_batch` parameter to laio_co_submit() 

This new parameter can be used by block devices to limit the
Linux AIO batch size more than the limit set by the AIO context.

file-posix backend supports this, passing its `aio-max-batch` option
previously added.

Add an helper function to calculate the maximum batch size.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20211026162346.253081-3-sgarzare@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
master
Stefano Garzarella 2021-10-26 18:23:45 +02:00 committed by Kevin Wolf
parent 684960d462
commit 512da21101
3 changed files with 26 additions and 10 deletions
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3
block/file-posix.c
View File

@ -2066,7 +2066,8 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
} else if (s->use_linux_aio) {
LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
assert(qiov->size == bytes);
return laio_co_submit(bs, aio, s->fd, offset, qiov, type);
return laio_co_submit(bs, aio, s->fd, offset, qiov, type,
s->aio_max_batch);
#endif
}

30
block/linux-aio.c
View File

@ -334,6 +334,23 @@ static void ioq_submit(LinuxAioState *s)
}
}
static uint64_t laio_max_batch(LinuxAioState *s, uint64_t dev_max_batch)
{
uint64_t max_batch = s->aio_context->aio_max_batch ?: DEFAULT_MAX_BATCH;
/*
* AIO context can be shared between multiple block devices, so
* `dev_max_batch` allows reducing the batch size for latency-sensitive
* devices.
*/
max_batch = MIN_NON_ZERO(dev_max_batch, max_batch);
/* limit the batch with the number of available events */
max_batch = MIN_NON_ZERO(MAX_EVENTS - s->io_q.in_flight, max_batch);
return max_batch;
}
void laio_io_plug(BlockDriverState *bs, LinuxAioState *s)
{
s->io_q.plugged++;
@ -349,15 +366,11 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s)
}
static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
int type)
int type, uint64_t dev_max_batch)
{
LinuxAioState *s = laiocb->ctx;
struct iocb *iocbs = &laiocb->iocb;
QEMUIOVector *qiov = laiocb->qiov;
int64_t max_batch = s->aio_context->aio_max_batch ?: DEFAULT_MAX_BATCH;
/* limit the batch with the number of available events */
max_batch = MIN_NON_ZERO(MAX_EVENTS - s->io_q.in_flight, max_batch);
switch (type) {
case QEMU_AIO_WRITE:
@ -378,7 +391,7 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
s->io_q.in_queue++;
if (!s->io_q.blocked &&
(!s->io_q.plugged ||
s->io_q.in_queue >= max_batch)) {
s->io_q.in_queue >= laio_max_batch(s, dev_max_batch))) {
ioq_submit(s);
}
@ -386,7 +399,8 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
}
int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
uint64_t offset, QEMUIOVector *qiov, int type)
uint64_t offset, QEMUIOVector *qiov, int type,
uint64_t dev_max_batch)
{
int ret;
struct qemu_laiocb laiocb = {
@ -398,7 +412,7 @@ int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
.qiov = qiov,
};
ret = laio_do_submit(fd, &laiocb, offset, type);
ret = laio_do_submit(fd, &laiocb, offset, type, dev_max_batch);
if (ret < 0) {
return ret;
}

3
include/block/raw-aio.h
View File

@ -51,7 +51,8 @@ typedef struct LinuxAioState LinuxAioState;
LinuxAioState *laio_init(Error **errp);
void laio_cleanup(LinuxAioState *s);
int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
uint64_t offset, QEMUIOVector *qiov, int type);
uint64_t offset, QEMUIOVector *qiov, int type,
uint64_t dev_max_batch);
void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context);
void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context);
void laio_io_plug(BlockDriverState *bs, LinuxAioState *s);