On 25/02/2015 06:45, Fam Zheng wrote:
> On Fri, 02/20 17:26, Paolo Bonzini wrote:
>> This is the first step in pushing down acquire/release, and will let
>> rfifolock drop the contention callback feature.
>>
>> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
>> ---
>> aio-posix.c | 9 +++++++++
>> aio-win32.c | 8 ++++++++
>> include/block/aio.h | 15 ++++++++-------
>> 3 files changed, 25 insertions(+), 7 deletions(-)
>>
>> diff --git a/aio-posix.c b/aio-posix.c
>> index 4a30b77..292ae84 100644
>> --- a/aio-posix.c
>> +++ b/aio-posix.c
>> @@ -238,6 +238,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
>> bool progress;
>> int64_t timeout;
>>
>> + aio_context_acquire(ctx);
>> was_dispatching = ctx->dispatching;
>> progress = false;
>>
>> @@ -267,7 +268,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
>> timeout = blocking ? aio_compute_timeout(ctx) : 0;
>>
>> /* wait until next event */
>> + if (timeout) {
>> + aio_context_release(ctx);
>> + }
>> ret = qemu_poll_ns((GPollFD *)pollfds, npfd, timeout);
>> + if (timeout) {
>> + aio_context_acquire(ctx);
>> + }
>>
>> /* if we have any readable fds, dispatch event */
>> if (ret > 0) {
>> @@ -285,5 +292,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
>> }
>>
>> aio_set_dispatching(ctx, was_dispatching);
>> + aio_context_release(ctx);
>> +
>> return progress;
>> }
>> diff --git a/aio-win32.c b/aio-win32.c
>> index e6f4ced..233d8f5 100644
>> --- a/aio-win32.c
>> +++ b/aio-win32.c
>> @@ -283,6 +283,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
>> int count;
>> int timeout;
>>
>> + aio_context_acquire(ctx);
>> have_select_revents = aio_prepare(ctx);
>> if (have_select_revents) {
>> blocking = false;
>> @@ -323,7 +324,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
>>
>> timeout = blocking
>> ? qemu_timeout_ns_to_ms(aio_compute_timeout(ctx)) : 0;
>> + if (timeout) {
>> + aio_context_release(ctx);
>
> Why are the unlock/lock pairs around poll conditional?
Both iothread.c and os_host_main_loop_wait are doing it, IIRC it was
measurably faster.
In particular, iothread.c was completely avoiding acquire/release around
non-blocking aio_poll and this patch does not have exactly the same behavior,
but it is trying to be close:
- aio_context_acquire(iothread->ctx);
- blocking = true;
- while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
- /* Progress was made, keep going */
- blocking = false;
- }
- aio_context_release(iothread->ctx);
The exact same behavior can be done easily directly in aio_poll, for this
RFC I'm keeping the code a little simpler.
Paolo
>
> Fam
>
>> + }
>> ret = WaitForMultipleObjects(count, events, FALSE, timeout);
>> + if (timeout) {
>> + aio_context_acquire(ctx);
>> + }
>> aio_set_dispatching(ctx, true);
>>
>> if (first && aio_bh_poll(ctx)) {
