Hi Rusty, On Mon, Jan 27, 2014 at 10:18 PM, Rusty Russell <[email protected]>wrote:
> Leandro Dorileo <[email protected]> writes: > > Cchange init_vqs() to avoid calling twice the virtio_has_feature() > > - attempting to find out if VIRTIO_BALLOON_F_STATS_VQ feature was > negotiated - > > consequently we prevent unnecessarily running the drivers' feature_table > more > > than needed. > > > > Signed-off-by: Leandro Dorileo <[email protected]> > > Hi Leandro, > > This seems like a premature optimization. The current code is > fairly clear, and there's no performance issue with init_vqs. > > Indeed, rethinking the patch and reviewing the code path it seems to be no gain, It's just called on probe and restore operations. As you said a premature optimization. Thanks... > Am I missing something? > Rusty. > > > --- > > drivers/virtio/virtio_balloon.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/virtio/virtio_balloon.c > b/drivers/virtio/virtio_balloon.c > > index 34bdaba..41771c1 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -320,19 +320,21 @@ static int init_vqs(struct virtio_balloon *vb) > > vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, > stats_request }; > > const char *names[] = { "inflate", "deflate", "stats" }; > > int err, nvqs; > > + bool stats; > > > > /* > > * We expect two virtqueues: inflate and deflate, and > > * optionally stat. > > */ > > - nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 > : 2; > > + stats = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ); > > + nvqs = stats ? 3 : 2; > > err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, > names); > > if (err) > > return err; > > > > vb->inflate_vq = vqs[0]; > > vb->deflate_vq = vqs[1]; > > - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > > + if (stats) { > > struct scatterlist sg; > > vb->stats_vq = vqs[2]; > > > > -- > > 1.8.5.3 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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