Commit 7d506c90 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Stefan Hajnoczi
Browse files

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: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Message-id: 20170112180800.21085-11-pbonzini@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 7c690fd1

async.c

+9 −1
Original line number Diff line number Diff line
@@ -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;

}