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

[Eric Dumazet <eric.dumazet@xxxxxxxxx>]

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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