On Fri, Apr 20, 2018 at 12:42:10 +0800, Peter Xu wrote:
> Put all the shared qemu-thread implementations into these files. The
> header should be internal to qemu-thread but not for qemu-thread users.
>
> Introduce some hooks correspondingly for the shared part. Note that in
> qemu_mutex_unlock_impl() we moved the call before unlock operation which
> should make more sense. And we don't need qemu_mutex_post_unlock() hook.
>
> Currently the hooks only calls the tracepoints.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
(snip)
> - trace_qemu_mutex_lock(mutex, file, line);
> -
> + qemu_mutex_pre_lock(mutex, file, line);
> err = pthread_mutex_lock(&mutex->lock);
> if (err)
> error_exit(err, __func__);
> -
> - trace_qemu_mutex_locked(mutex, file, line);
> + qemu_mutex_post_lock(mutex, file, line);
> }
I see the value in consolidating these calls. However, having a separate
object means that this adds two function calls to mutex_lock. This
significantly reduces performance, even without --enable-debug-mutex:
- Before:
$ taskset -c 0 tests/atomic_add-bench -n 1 -m
Parameters:
# of threads: 1
duration: 1
ops' range: 1024
Results:
Duration: 1 s
Throughput: 57.24 Mops/s
Throughput/thread: 57.24 Mops/s/thread
- After:
$ taskset -c 0 tests/atomic_add-bench -n 1 -m
Parameters:
# of threads: 1
duration: 1
ops' range: 1024
Results:
Duration: 1 s
Throughput: 49.22 Mops/s
Throughput/thread: 49.22 Mops/s/thread
So either inlines/macros should be used instead -- I'd prefer
inlines but I'm not sure they'll work with the tracing calls.
I think you should cherry-pick this patch[1] and add it to the
series -- it'll let you make sure the series does not affect
performance.
Cheers,
Emilio
[1] https://github.com/cota/qemu/commit/f04f34df
