Re: [PATCH] virtio-blk: Disable callback in virtblk_done()

On Thu, Sep 27, 2012 at 12:01 PM, Paolo Bonzini [off-list ref] wrote:

Il 27/09/2012 02:10, Rusty Russell ha scritto:

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+        do {
+                virtqueue_disable_cb(vq);
+                while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
+                        if (vbr->bio) {
+                                virtblk_bio_done(vbr);
+                                bio_done = true;
+                        } else {
+                                virtblk_request_done(vbr);
+                                req_done = true;
+                        }
                 }
-        }
+        } while (!virtqueue_enable_cb(vq));
         /* In case queue is stopped waiting for more buffers. */
         if (req_done)
                 blk_start_queue(vblk->disk->queue);

Fascinating.  Please just confirm that VIRTIO_RING_F_EVENT_IDX is
enabled?

Yeah, it's a nice and cheap trick.  Stefan, I see that you had this in
virtio-scsi since even before I picked it up.  Do you remember how you
came up with it?

I've played with disable_cb/enable_cb previously in virtio-blk and
virtio-scsi when aliguori had suggested reducing notifies.  I
definitely didn't invent it :).

Stefan