On Wed, Jan 23, 2013 at 09:46:47PM +0100, Romain Francoise wrote:
> Creating a vhost-net device allocates an object large enough (34320 bytes
> on x86-64) to trigger an order-4 allocation, which may fail if memory if
> fragmented:
>
> libvirtd: page allocation failure: order:4, mode:0x2000d0
> ...
> SLAB: Unable to allocate memory on node 0 (gfp=0xd0)
> cache: size-65536, object size: 65536, order: 4
> node 0: slabs: 8/8, objs: 8/8, free: 0
>
> In that situation, rather than forcing the caller to use regular
> virtio-net, try to allocate the descriptor with vmalloc().
>
> Signed-off-by: Romain Francoise <romain@xxxxxxxxxxxxx>
Thanks for the patch.
Hmm, I haven't seen this.
Maybe we should try and reduce our memory usage,
I will look into this.
> ---
> drivers/vhost/net.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ebd08b2..1ded79b 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -18,6 +18,7 @@
> #include <linux/rcupdate.h>
> #include <linux/file.h>
> #include <linux/slab.h>
> +#include <linux/vmalloc.h>
>
> #include <linux/net.h>
> #include <linux/if_packet.h>
> @@ -603,12 +604,23 @@ static void handle_rx_net(struct vhost_work *work)
> handle_rx(net);
> }
>
> +static void vhost_net_kvfree(void *addr)
> +{
> + if (is_vmalloc_addr(addr))
> + vfree(addr);
> + else
> + kfree(addr);
> +}
> +
> static int vhost_net_open(struct inode *inode, struct file *f)
> {
> - struct vhost_net *n = kmalloc(sizeof *n, GFP_KERNEL);
> + struct vhost_net *n;
> struct vhost_dev *dev;
> int r;
>
> + n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN);
> + if (!n)
> + n = vmalloc(sizeof *n);
> if (!n)
> return -ENOMEM;
>
> @@ -617,7 +629,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;
> r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX);
> if (r < 0) {
> - kfree(n);
> + vhost_net_kvfree(n);
> return r;
> }
>
> @@ -719,7 +731,7 @@ static int vhost_net_release(struct inode *inode, struct file *f)
> /* We do an extra flush before freeing memory,
> * since jobs can re-queue themselves. */
> vhost_net_flush(n);
> - kfree(n);
> + vhost_net_kvfree(n);
> return 0;
> }
>
> --
> 1.8.1.1
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