linux-kernel - [PATCH v4 2/3] virtio-balloon: improve update_balloon_size

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Message-Id: <1546923005-40517-3-git-send-email-wei.w.wang@intel.com>
Date:   Tue,  8 Jan 2019 12:50:04 +0800
From:   Wei Wang <wei.w.wang@...el.com>
To:     virtio-dev@...ts.oasis-open.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        kvm@...r.kernel.org, mst@...hat.com, cohuck@...hat.com
Cc:     borntraeger@...ibm.com, pbonzini@...hat.com, dgilbert@...hat.com,
        wei.w.wang@...el.com, pasic@...ux.ibm.com
Subject: [PATCH v4 2/3] virtio-balloon: improve update_balloon_size_func

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@...el.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@...ibm.com>
---
 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 45d32f5..d48c12c 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