[v3,2/3] virtio-balloon: improve update_balloon_size_func
diff mbox series

Message ID 1546844466-38079-3-git-send-email-wei.w.wang@intel.com
State Superseded
Headers show
Series
  • virtio-balloon: tweak config_changed
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Commit Message

Wei Wang Jan. 7, 2019, 7:01 a.m. UTC
There is no need to update the balloon actual register when there is no
ballooning request. This patch avoids update_balloon_size when diff is 0.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
---
 drivers/virtio/virtio_balloon.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Michael S. Tsirkin Jan. 15, 2019, 1 a.m. UTC | #1
On Mon, Jan 07, 2019 at 03:01:05PM +0800, Wei Wang wrote:
> There is no need to update the balloon actual register when there is no
> ballooning request. This patch avoids update_balloon_size when diff is 0.
> 
> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>

It sounds reasonable but it does have a side effect of
not writing into actual anymore.

I am not sure actual never can get out of sync as a result.

So better deferred, pls send this in the next merge window.




> ---
>  drivers/virtio/virtio_balloon.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index fb12fe2..e33dc8e 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -457,9 +457,12 @@ static void update_balloon_size_func(struct work_struct *work)
>  			  update_balloon_size_work);
>  	diff = towards_target(vb);
>  
> +	if (!diff)
> +		return;
> +
>  	if (diff > 0)
>  		diff -= fill_balloon(vb, diff);
> -	else if (diff < 0)
> +	else
>  		diff += leak_balloon(vb, -diff);
>  	update_balloon_size(vb);
>  
> -- 
> 2.7.4
Wei Wang Jan. 15, 2019, 2:18 a.m. UTC | #2
On 01/15/2019 09:00 AM, Michael S. Tsirkin wrote:
> On Mon, Jan 07, 2019 at 03:01:05PM +0800, Wei Wang wrote:
>> There is no need to update the balloon actual register when there is no
>> ballooning request. This patch avoids update_balloon_size when diff is 0.
>>
>> Signed-off-by: Wei Wang <wei.w.wang@intel.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> It sounds reasonable but it does have a side effect of
> not writing into actual anymore.
>
> I am not sure actual never can get out of sync as a result.
>
> So better deferred, pls send this in the next merge window.
>

No problem, it's not urgent to me.

Best,
Wei

Patch
diff mbox series

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index fb12fe2..e33dc8e 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -457,9 +457,12 @@  static void update_balloon_size_func(struct work_struct *work)
 			  update_balloon_size_work);
 	diff = towards_target(vb);
 
+	if (!diff)
+		return;
+
 	if (diff > 0)
 		diff -= fill_balloon(vb, diff);
-	else if (diff < 0)
+	else
 		diff += leak_balloon(vb, -diff);
 	update_balloon_size(vb);