linux-kernel - Re: Page allocation failures in guest

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Message-Id: <200908121626.31531.rusty@rustcorp.com.au>
Date:	Wed, 12 Aug 2009 16:26:30 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Avi Kivity <avi@...hat.com>
Cc:	Pierre Ossman <drzeus-list@...eus.cx>,
	Minchan Kim <minchan.kim@...il.com>, kvm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Wu Fengguang <fengguang.wu@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, netdev@...r.kernel.org
Subject: Re: Page allocation failures in guest

On Wed, 12 Aug 2009 03:11:21 pm Avi Kivity wrote:
> > +	/* In theory, this can happen: if we don't get any buffers in
> > +	 * we will*never*  try to fill again.  Sleeping in keventd if
> > +	 * bad, but that is worse. */
> > +	if (still_empty) {
> > +		msleep(100);
> > +		schedule_work(&vi->refill);
> > +	}
> > +}
> > + 
> 
> schedule_delayed_work()?

Hmm, might as well, although this is v. unlikely to happen.

Thanks,
Rusty.

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -72,7 +72,7 @@ struct virtnet_info
 	struct sk_buff_head send;
 
 	/* Work struct for refilling if we run low on memory. */
-	struct work_struct refill;
+	struct delayed_work refill;
 	
 	/* Chain pages by the private ptr. */
 	struct page *pages;
@@ -402,19 +402,16 @@ static void refill_work(struct work_stru
 	struct virtnet_info *vi;
 	bool still_empty;
 
-	vi = container_of(work, struct virtnet_info, refill);
+	vi = container_of(work, struct virtnet_info, refill.work);
 	napi_disable(&vi->napi);
 	try_fill_recv(vi, GFP_KERNEL);
 	still_empty = (vi->num == 0);
 	napi_enable(&vi->napi);
 
 	/* In theory, this can happen: if we don't get any buffers in
-	 * we will *never* try to fill again.  Sleeping in keventd if
-	 * bad, but that is worse. */
-	if (still_empty) {
-		msleep(100);
-		schedule_work(&vi->refill);
-	}
+	 * we will *never* try to fill again. */
+	if (still_empty)
+		schedule_delayed_work(&vi->refill, HZ/2);
 }
 
 static int virtnet_poll(struct napi_struct *napi, int budget)
@@ -434,7 +431,7 @@ again:
 
 	if (vi->num < vi->max / 2) {
 		if (!try_fill_recv(vi, GFP_ATOMIC))
-			schedule_work(&vi->refill);
+			schedule_delayed_work(&vi->refill, 0);
 	}
 
 	/* Out of packets? */
@@ -925,7 +922,7 @@ static int virtnet_probe(struct virtio_d
 	vi->vdev = vdev;
 	vdev->priv = vi;
 	vi->pages = NULL;
-	INIT_WORK(&vi->refill, refill_work);
+	INIT_DELAYED_WORK(&vi->refill, refill_work);
 
 	/* If they give us a callback when all buffers are done, we don't need
 	 * the timer. */
@@ -991,7 +988,7 @@ static int virtnet_probe(struct virtio_d
 
 unregister:
 	unregister_netdev(dev);
-	cancel_work_sync(&vi->refill);
+	cancel_delayed_work_sync(&vi->refill);
 free_vqs:
 	vdev->config->del_vqs(vdev);
 free:
@@ -1020,7 +1017,7 @@ static void virtnet_remove(struct virtio
 	BUG_ON(vi->num != 0);
 
 	unregister_netdev(vi->dev);
-	cancel_work_sync(&vi->refill);
+	cancel_delayed_work_sync(&vi->refill);
 
 	vdev->config->del_vqs(vi->vdev);
 
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