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| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-07-21 16:07:53 +0200 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2015-07-22 12:41:40 +0100 |
| commit | 05e514b1d4d5bd4209e2c8bbc76ff05c85a235f3 (patch) | |
| tree | 1768698d814f687fc322e365c672ddd94c14d55b /qemu-img-cmds.hx | |
| parent | 21a03d17f2edb1e63f7137d97ba355cc6f19d79f (diff) | |
AioContext: optimize clearing the EventNotifier
It is pretty rare for aio_notify to actually set the EventNotifier. It
can happen with worker threads such as thread-pool.c's, but otherwise it
should never be set thanks to the ctx->notify_me optimization. The
previous patch, unfortunately, added an unconditional call to
event_notifier_test_and_clear; now add a userspace fast path that
avoids the call.
Note that it is not possible to do the same with event_notifier_set;
it would break, as proved (again) by the included formal model.
This patch survived over 3000 reboots on aarch64 KVM.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Message-id: 1437487673-23740-7-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'qemu-img-cmds.hx')
0 files changed, 0 insertions, 0 deletions