From bd738e0bbc2fec04c928959e8e7e99af03024782 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Tue, 9 Oct 2018 08:16:51 +0100 Subject: [PATCH 07/17] aio-posix: do skip system call if ctx->notifier polling succeeds RH-Author: Fam Zheng Message-id: <20181009081651.15463-6-famz@redhat.com> Patchwork-id: 82449 O-Subject: [RHEL8/rhel qemu-kvm PATCH 5/5] aio-posix: do skip system call if ctx->notifier polling succeeds Bugzilla: 1632622 RH-Acked-by: Thomas Huth RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Danilo de Paula From: Paolo Bonzini BZ: 1632622 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: 70232b5253a3c4e03ed1ac47ef9246a8ac66c6fa Signed-off-by: Paolo Bonzini Message-Id: <20180912171040.1732-4-pbonzini@redhat.com> Reviewed-by: Fam Zheng Signed-off-by: Fam Zheng (cherry picked from commit cfeb35d6774b2e936046aa9923217818bd160299) Signed-off-by: Fam Zheng Signed-off-by: Danilo C. L. de Paula --- util/aio-posix.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/util/aio-posix.c b/util/aio-posix.c index 1b17597..357de8a 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -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. */ -- 1.8.3.1