netdev - Re: [PATCH net-next] xen-netback: allocate xenvif arrays using vzalloc.

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Date:	Tue, 29 Oct 2013 16:32:12 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joby Poriyath <joby.poriyath@...rix.com>
Cc:	netdev@...r.kernel.org, wei.liu2@...rix.com,
	ian.campbell@...rix.com, xen-devel@...ts.xen.org,
	andrew.bennieston@...rix.com, david.vrabel@...rix.com,
	malcolm.crossley@...rix.com
Subject: Re: [PATCH net-next] xen-netback: allocate xenvif arrays using
 vzalloc.

On Tue, 2013-10-29 at 16:24 -0700, Eric Dumazet wrote:
> On Tue, 2013-10-29 at 18:46 +0000, Joby Poriyath wrote:
> > On Tue, Oct 29, 2013 at 08:43:50AM -0700, Eric Dumazet wrote:
> > > On Tue, 2013-10-29 at 15:27 +0000, Joby Poriyath wrote:
> > > > This will reduce memory pressure when allocating struct xenvif.
> > > > 
> > > > The size of xenvif struct has increased from 168 to 36632 bytes (on x86-32).
> > > > See commit b3f980bd827e6e81a050c518d60ed7811a83061d. This resulted in
> > > > occasional netdev allocation failure in dom0 with 752MiB RAM, due to
> > > > fragmented memory.
> > > 
> > > This looks overkill. 
> > > 
> > > Replacing a single allocation of ~36 KB into 5 vmalloc() looks like you
> > > did not really tried other things...
> > > 
> > > This should be done generically in alloc_netdev_mqs()
> > 
> > Sorry Eric, I didn't quite understand how this can be generically done.
> > 
> > The netback interfaces are tied to the Xen guests (VMs) and these are created 
> > when guests are started and deleted when guest are halted.
> 
> They are created by alloc_netdev_mqs()

Something like the following should be fine.



diff --git a/net/core/dev.c b/net/core/dev.c
index 0054c8c..874a57a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6239,7 +6239,9 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 	/* ensure 32-byte alignment of whole construct */
 	alloc_size += NETDEV_ALIGN - 1;
 
-	p = kzalloc(alloc_size, GFP_KERNEL);
+	p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
+	if (!p)
+		p = vzalloc(alloc_size);
 	if (!p)
 		return NULL;
 
@@ -6302,7 +6304,10 @@ free_pcpu:
 #endif
 
 free_p:
-	kfree(p);
+	if (is_vmalloc_addr(p))
+		vfree(p);
+	else
+		kfree(p);
 	return NULL;
 }
 EXPORT_SYMBOL(alloc_netdev_mqs);
@@ -6339,7 +6344,12 @@ void free_netdev(struct net_device *dev)
 
 	/*  Compatibility with error handling in drivers */
 	if (dev->reg_state == NETREG_UNINITIALIZED) {
-		kfree((char *)dev - dev->padded);
+		char *addr = (char *)dev - dev->padded;
+
+		if (is_vmalloc_addr(addr))
+			vfree(addr);
+		else
+			kfree(addr);
 		return;
 	}
 
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index d954b56..406c54b 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1259,11 +1259,16 @@ exit:
 static void netdev_release(struct device *d)
 {
 	struct net_device *dev = to_net_dev(d);
+	char *addr;
 
 	BUG_ON(dev->reg_state != NETREG_RELEASED);
 
 	kfree(dev->ifalias);
-	kfree((char *)dev - dev->padded);
+	addr = (char *)dev - dev->padded;
+	if (is_vmalloc_addr(addr))
+		vfree(addr);
+	else
+		kfree(addr);
 }
 
 static const void *net_namespace(struct device *d)


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