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authorStefano Garzarella <sgarzare@redhat.com>2021-10-26 18:23:45 +0200
committerKevin Wolf <kwolf@redhat.com>2021-11-02 13:03:35 +0100
commit512da211010700cdbfaab45c8980ca88958a4ab8 (patch)
tree8054868338e2b4c4f12e58e010e60a059ba91f1c /block/linux-aio.c
parent684960d46267d6e6443b39ee98b3a95632ba8dc6 (diff)
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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>
Diffstat (limited to 'block/linux-aio.c')
-rw-r--r--block/linux-aio.c30
1 files changed, 22 insertions, 8 deletions
diff --git a/block/linux-aio.c b/block/linux-aio.c
index 0dab507..88b44fe 100644
--- a/block/linux-aio.c
+++ b/block/linux-aio.c
@@ -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;
}