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| author | Paolo Bonzini <pbonzini@redhat.com> | 2016-10-06 11:39:12 +0200 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2016-10-31 00:21:43 +0200 |
| commit | 948a8ac2964f39161ebf832dea0aa1ced90101bb (patch) | |
| tree | b74d1bb2f74384b1a57209bf2d0f453de3968347 | |
| parent | d3c3589b8b3cd4fabf4cd137facb42a7fb36bd7f (diff) | |
| download | linux-948a8ac2964f39161ebf832dea0aa1ced90101bb.tar.bz2 | |
ringtest: poll for new buffers once before updating event index
Updating the event index has a memory barrier and causes more work
on the other side to actually signal the event. It is unnecessary
if a new buffer has already appeared on the ring, so poll once before
doing the update.
The effect of this on the 0.9 ring implementation is pretty much
invisible, but on the new-style ring it provides a consistent 3%
performance improvement.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
| -rw-r--r-- | tools/virtio/ringtest/main.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/virtio/ringtest/main.c b/tools/virtio/ringtest/main.c index b00ecd619969..f31353fac541 100644 --- a/tools/virtio/ringtest/main.c +++ b/tools/virtio/ringtest/main.c @@ -147,7 +147,7 @@ static void __attribute__((__flatten__)) run_guest(void) assert(completed <= bufs); assert(started <= bufs); if (do_sleep) { - if (enable_call()) + if (used_empty() && enable_call()) wait_for_call(); } else { poll_used(); @@ -172,7 +172,7 @@ static void __attribute__((__flatten__)) run_host(void) for (;;) { if (do_sleep) { - if (enable_kick()) + if (avail_empty() && enable_kick()) wait_for_kick(); } else { poll_avail(); |