* Re: [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs()
[not found] <1390679972-1406-1-git-send-email-l@dorileo.org>
@ 2014-01-28 0:18 ` Rusty Russell
2014-01-28 1:27 ` Leandro Dorileo
2014-01-28 2:06 ` Leandro Dorileo
0 siblings, 2 replies; 4+ messages in thread
From: Rusty Russell @ 2014-01-28 0:18 UTC (permalink / raw)
To: Leandro Dorileo, linux-kernel; +Cc: virtio-dev, mst, virtualization
Leandro Dorileo <l@dorileo.org> 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 <l@dorileo.org>
Hi Leandro,
This seems like a premature optimization. The current code is
fairly clear, and there's no performance issue with init_vqs.
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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs()
2014-01-28 0:18 ` [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs() Rusty Russell
@ 2014-01-28 1:27 ` Leandro Dorileo
2014-01-28 2:06 ` Leandro Dorileo
1 sibling, 0 replies; 4+ messages in thread
From: Leandro Dorileo @ 2014-01-28 1:27 UTC (permalink / raw)
To: Rusty Russell; +Cc: virtio-dev, mst, linux-kernel, virtualization
[-- Attachment #1.1: Type: text/plain, Size: 2395 bytes --]
Hi Rusty,
On Mon, Jan 27, 2014 at 10:18 PM, Rusty Russell <rusty@rustcorp.com.au>wrote:
> Leandro Dorileo <l@dorileo.org> 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 <l@dorileo.org>
>
> 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
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>
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs()
2014-01-28 0:18 ` [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs() Rusty Russell
2014-01-28 1:27 ` Leandro Dorileo
@ 2014-01-28 2:06 ` Leandro Dorileo
1 sibling, 0 replies; 4+ messages in thread
From: Leandro Dorileo @ 2014-01-28 2:06 UTC (permalink / raw)
To: Rusty Russell; +Cc: virtio-dev, mst, linux-kernel, virtualization
Hi Rusty,
On Tue, Jan 28, 2014 at 10:48:31AM +1030, Rusty Russell wrote:
> Leandro Dorileo <l@dorileo.org> 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 <l@dorileo.org>
>
> 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 majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Leandro Dorileo
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs()
@ 2014-01-25 19:59 Leandro Dorileo
0 siblings, 0 replies; 4+ messages in thread
From: Leandro Dorileo @ 2014-01-25 19:59 UTC (permalink / raw)
To: linux-kernel; +Cc: virtio-dev, mst, virtualization
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 <l@dorileo.org>
---
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
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2014-01-28 0:18 ` [PATCH] virtio_balloon: don't call virtio_has_feature() twice on init_vqs() Rusty Russell
2014-01-28 1:27 ` Leandro Dorileo
2014-01-28 2:06 ` Leandro Dorileo
2014-01-25 19:59 Leandro Dorileo
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