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async: optimize aio_bh_poll

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Avoid entering the slow path of qemu_lockcnt_dec_and_lock if
no bottom half has to be deleted.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170112180800.21085-11-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-01-12 19:08:00 +01:00 committed by Stefan Hajnoczi
parent 7c690fd193
commit 7d506c90af
1 changed files with 9 additions and 1 deletions
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10
async.c
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@ -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;
}