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author | Stefan Hajnoczi <stefanha@redhat.com> | 2013-11-26 16:18:00 +0100 |
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committer | Stefan Hajnoczi <stefanha@redhat.com> | 2013-12-06 16:53:51 +0100 |
commit | 0b06ef3bdd17742ae50c0662d3fe8ed944648890 (patch) | |
tree | 536df3da25a5f0180b527122ffb5396d6815354c | |
parent | ac95acdb8e0876fa489bd31a48e8ecd6ef901d67 (diff) | |
download | qemu-0b06ef3bdd17742ae50c0662d3fe8ed944648890.zip qemu-0b06ef3bdd17742ae50c0662d3fe8ed944648890.tar.gz qemu-0b06ef3bdd17742ae50c0662d3fe8ed944648890.tar.bz2 |
block: clean up bdrv_drain_all() throttling comments
Since cc0681c45430a1f1a4c2d06e9499b7775afc9a18 ("block: Enable the new
throttling code in the block layer.") bdrv_drain_all() no longer spins.
The code used to look as follows:
do {
busy = qemu_aio_wait();
/* FIXME: We do not have timer support here, so this is effectively
* a busy wait.
*/
QTAILQ_FOREACH(bs, &bdrv_states, list) {
while (qemu_co_enter_next(&bs->throttled_reqs)) {
busy = true;
}
}
} while (busy);
Note that throttle requests are kicked but I/O throttling limits are
still in effect. The loop spins until the vm_clock time allows the
request to make progress and complete.
The new throttling code introduced bdrv_start_throttled_reqs(). This
function not only kicks throttled requests but also temporarily disables
throttling so requests can run.
The outdated FIXME comment can be removed. Also drop the busy = true
assignment since we overwrite it immediately afterwards.
Reviewed-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
-rw-r--r-- | block.c | 7 |
1 files changed, 1 insertions, 6 deletions
@@ -1557,13 +1557,8 @@ void bdrv_drain_all(void) BlockDriverState *bs; while (busy) { - /* FIXME: We do not have timer support here, so this is effectively - * a busy wait. - */ QTAILQ_FOREACH(bs, &bdrv_states, list) { - if (bdrv_start_throttled_reqs(bs)) { - busy = true; - } + bdrv_start_throttled_reqs(bs); } busy = bdrv_requests_pending_all(); |