[Qemu-devel] [PULL for-2.4 0/1] virtio-rng: reduce wakeups

[Qemu-devel] [PULL for-2.4 0/1] virtio-rng: reduce wakeups

[Amit Shah]

The following changes since commit 5b5e8cdd7da7a2214dd062afff5b866234aab228:

  Merge remote-tracking branch 'remotes/kraxel/tags/pull-usb-20150717-1' into staging (2015-07-17 12:39:12 +0100)

are available in the git repository at:

  https://git.kernel.org/pub/scm/virt/qemu/amit/virtio-rng.git tags/vrng-2.4

for you to fetch changes up to 621a20e08155179b1902c428361e80f41429f50d:

  virtio-rng: trigger timer only when guest requests for entropy (2015-07-17 19:05:16 +0530)

----------------------------------------------------------------
Fire timer only when required.  Brings down wakeups by a big number.

----------------------------------------------------------------

Pankaj Gupta (1):
  virtio-rng: trigger timer only when guest requests for entropy

 hw/virtio/virtio-rng.c         | 15 ++++++++-------
 include/hw/virtio/virtio-rng.h |  1 +
 2 files changed, 9 insertions(+), 7 deletions(-)

-- 
2.4.3

[Qemu-devel] [PULL for-2.4 1/1] virtio-rng: trigger timer only when guest requests for entropy

[Amit Shah]

From: Pankaj Gupta <pagupta@redhat.com>

This patch triggers timer only when guest requests for
entropy. As soon as first request from guest for entropy
comes we set the timer. Timer bumps up the quota value
when it gets triggered.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Message-Id: <1436962608-9961-2-git-send-email-pagupta@redhat.com>

[Re-worded patch subject, removed extra whitespace -- Amit]

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 hw/virtio/virtio-rng.c         | 15 ++++++++-------
 include/hw/virtio/virtio-rng.h |  1 +
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index 740ed31..6e5f022 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -77,6 +77,12 @@ static void virtio_rng_process(VirtIORNG *vrng)
         return;
     }
 
+    if (vrng->activate_timer) {
+        timer_mod(vrng->rate_limit_timer,
+                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
+        vrng->activate_timer = false;
+    }
+
     if (vrng->quota_remaining < 0) {
         quota = 0;
     } else {
@@ -138,8 +144,7 @@ static void check_rate_limit(void *opaque)
 
     vrng->quota_remaining = vrng->conf.max_bytes;
     virtio_rng_process(vrng);
-    timer_mod(vrng->rate_limit_timer,
-                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
+    vrng->activate_timer = true;
 }
 
 static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
@@ -195,13 +200,9 @@ static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
 
     vrng->vq = virtio_add_queue(vdev, 8, handle_input);
     vrng->quota_remaining = vrng->conf.max_bytes;
-
     vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                                check_rate_limit, vrng);
-
-    timer_mod(vrng->rate_limit_timer,
-                   qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
-
+    vrng->activate_timer = true;
     register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
                     virtio_rng_load, vrng);
 }
diff --git a/include/hw/virtio/virtio-rng.h b/include/hw/virtio/virtio-rng.h
index 0316488..3f07de7 100644
--- a/include/hw/virtio/virtio-rng.h
+++ b/include/hw/virtio/virtio-rng.h
@@ -44,6 +44,7 @@ typedef struct VirtIORNG {
      */
     QEMUTimer *rate_limit_timer;
     int64_t quota_remaining;
+    bool activate_timer;
 } VirtIORNG;
 
 #endif
-- 
2.4.3

Re: [Qemu-devel] [PULL for-2.4 0/1] virtio-rng: reduce wakeups

[Peter Maydell]

On 17 July 2015 at 14:49, Amit Shah <amit.shah@redhat.com> wrote:
> The following changes since commit 5b5e8cdd7da7a2214dd062afff5b866234aab228:
>
>   Merge remote-tracking branch 'remotes/kraxel/tags/pull-usb-20150717-1' into staging (2015-07-17 12:39:12 +0100)
>
> are available in the git repository at:
>
>   https://git.kernel.org/pub/scm/virt/qemu/amit/virtio-rng.git tags/vrng-2.4
>
> for you to fetch changes up to 621a20e08155179b1902c428361e80f41429f50d:
>
>   virtio-rng: trigger timer only when guest requests for entropy (2015-07-17 19:05:16 +0530)
>
> ----------------------------------------------------------------
> Fire timer only when required.  Brings down wakeups by a big number.

Applied, thanks.

-- PMM