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aio-posix: do skip system call if ctx->notifier polling succeeds

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Commit 70232b5253 ("aio-posix: Don't count ctx->notifier as progress when
2018-08-15), by not reporting progress, causes aio_poll to execute the
system call when polling succeeds because of ctx->notifier.  This introduces
latency before the call to aio_bh_poll() and negates the advantages of
polling, unfortunately.

The fix builds on the previous patch, separating the effect of polling on
the timeout from the progress reported to aio_poll().  ctx->notifier
does zero the timeout, causing the caller to skip the system call,
but it does not report progress, so that the bug fix of commit 70232b5253
still stands.

Fixes: 70232b5253
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180912171040.1732-4-pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Paolo Bonzini
2018-09-26 10:46:21 +08:00
committed by Fam Zheng
parent e30cffa04d
commit cfeb35d677
1 changed files with 4 additions and 3 deletions
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util/aio-posix.c
+4 -3
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@@ -498,10 +498,11 @@ static bool run_poll_handlers_once(AioContext *ctx, int64_t *timeout)
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
if (!node->deleted && node->io_poll &&
aio_node_check(ctx, node->is_external) &&
node->io_poll(node->opaque) &&
node->opaque != &ctx->notifier) {
node->io_poll(node->opaque)) {
*timeout = 0;
progress = true;
if (node->opaque != &ctx->notifier) {
progress = true;
}
}
/* Caller handles freeing deleted nodes. Don't do it here. */