From 7d506c90afa47facdb993bc19c15863eef584f1d Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 12 Jan 2017 19:08:00 +0100 Subject: [PATCH] async: optimize aio_bh_poll Avoid entering the slow path of qemu_lockcnt_dec_and_lock if no bottom half has to be deleted. Reviewed-by: Stefan Hajnoczi Signed-off-by: Paolo Bonzini Reviewed-by: Fam Zheng Message-id: 20170112180800.21085-11-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi --- async.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/async.c b/async.c index 2305e11f26..0d218ab0e0 100644 --- a/async.c +++ b/async.c @@ -92,6 +92,7 @@ int aio_bh_poll(AioContext *ctx) { QEMUBH *bh, **bhp, *next; int ret; + bool deleted = false; qemu_lockcnt_inc(&ctx->list_lock); @@ -112,9 +113,17 @@ int aio_bh_poll(AioContext *ctx) bh->idle = 0; aio_bh_call(bh); } + if (bh->deleted) { + deleted = true; + } } /* remove deleted bhs */ + if (!deleted) { + qemu_lockcnt_dec(&ctx->list_lock); + return ret; + } + if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) { bhp = &ctx->first_bh; while (*bhp) { @@ -128,7 +137,6 @@ int aio_bh_poll(AioContext *ctx) } qemu_lockcnt_unlock(&ctx->list_lock); } - return ret; }