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mirror: do not flush every time the disks are synced
This puts a huge strain on the disks when there are many concurrent migrations. With this patch we only flush twice: just before issuing the event, and just before pivoting to the destination. If management will complete the job close to the BLOCK_JOB_READY event, the cost of the second flush should be small anyway. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161109162008.27287-2-pbonzini@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
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@ -615,6 +615,20 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
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return 0;
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}
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/* Called when going out of the streaming phase to flush the bulk of the
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* data to the medium, or just before completing.
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*/
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static int mirror_flush(MirrorBlockJob *s)
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{
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int ret = blk_flush(s->target);
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if (ret < 0) {
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if (mirror_error_action(s, false, -ret) == BLOCK_ERROR_ACTION_REPORT) {
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s->ret = ret;
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}
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}
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return ret;
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}
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static void coroutine_fn mirror_run(void *opaque)
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{
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MirrorBlockJob *s = opaque;
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@ -727,27 +741,23 @@ static void coroutine_fn mirror_run(void *opaque)
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should_complete = false;
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if (s->in_flight == 0 && cnt == 0) {
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trace_mirror_before_flush(s);
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ret = blk_flush(s->target);
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if (ret < 0) {
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if (mirror_error_action(s, false, -ret) ==
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BLOCK_ERROR_ACTION_REPORT) {
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goto immediate_exit;
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if (!s->synced) {
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if (mirror_flush(s) < 0) {
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/* Go check s->ret. */
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continue;
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}
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} else {
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/* We're out of the streaming phase. From now on, if the job
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* is cancelled we will actually complete all pending I/O and
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* report completion. This way, block-job-cancel will leave
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* the target in a consistent state.
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*/
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if (!s->synced) {
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block_job_event_ready(&s->common);
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s->synced = true;
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}
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should_complete = s->should_complete ||
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block_job_is_cancelled(&s->common);
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cnt = bdrv_get_dirty_count(s->dirty_bitmap);
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block_job_event_ready(&s->common);
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s->synced = true;
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}
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should_complete = s->should_complete ||
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block_job_is_cancelled(&s->common);
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cnt = bdrv_get_dirty_count(s->dirty_bitmap);
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}
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if (cnt == 0 && should_complete) {
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@ -765,7 +775,7 @@ static void coroutine_fn mirror_run(void *opaque)
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bdrv_drained_begin(bs);
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cnt = bdrv_get_dirty_count(s->dirty_bitmap);
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if (cnt > 0) {
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if (cnt > 0 || mirror_flush(s) < 0) {
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bdrv_drained_end(bs);
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continue;
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}
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