On Thu, Oct 09, 2014 at 08:41:23AM +0400, Dmitry Petuhov wrote:
> From: Michael S. Tsirkin <m...@redhat.com>
>
> upstream commit 23cc5a991c7a9fb7e6d6550e65cee4f4173111c5
>
> Michael Mueller provided a patch to reduce the size of
> vhost-net structure as some allocations could fail under
> memory pressure/fragmentation. We are still left with
> high order allocations though.
>
> This patch is handling the problem at the core level, allowing
> vhost structures to use vmalloc() if kmalloc() failed.
>
> As vmalloc() adds overhead on a critical network path, add __GFP_REPEAT
> to kzalloc() flags to do this fallback only when really needed.
>
> People are still looking at cleaner ways to handle the problem
> at the API level, probably passing in multiple iovecs.
> This hack seems consistent with approaches
> taken since then by drivers/vhost/scsi.c and net/core/dev.c
>
> Based on patch by Romain Francoise.
>
> Cc: Michael Mueller <m...@linux.vnet.ibm.com>
> Signed-off-by: Romain Francoise <rom...@orebokech.com>
> Acked-by: Michael S. Tsirkin <m...@redhat.com>
> [mityapetuhov: backport to v3.10: vhost_net_free() in one more place]
> Signed-off-by: Dmitry Petuhov <mityapetu...@gmail.com>
Sounds reasonable.
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> diff -uprN a/drivers/vhost/net.c b/drivers/vhost/net.c
> --- a/drivers/vhost/net.c 2014-10-09 06:45:08.336283258 +0400
> +++ b/drivers/vhost/net.c 2014-10-09 06:51:21.796266607 +0400
> @@ -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>
> @@ -707,18 +708,30 @@ static void handle_rx_net(struct vhost_w
> handle_rx(net);
> }
>
> +static void vhost_net_free(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;
> struct vhost_virtqueue **vqs;
> int r, i;
>
> - if (!n)
> - return -ENOMEM;
> + n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> + if (!n) {
> + n = vmalloc(sizeof *n);
> + if (!n)
> + return -ENOMEM;
> + }
> vqs = kmalloc(VHOST_NET_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
> if (!vqs) {
> - kfree(n);
> + vhost_net_free(n);
> return -ENOMEM;
> }
>
> @@ -737,7 +750,7 @@ static int vhost_net_open(struct inode *
> }
> r = vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
> if (r < 0) {
> - kfree(n);
> + vhost_net_free(n);
> kfree(vqs);
> return r;
> }
> @@ -840,7 +853,7 @@ static int vhost_net_release(struct inod
> * since jobs can re-queue themselves. */
> vhost_net_flush(n);
> kfree(n->dev.vqs);
> - kfree(n);
> + vhost_net_free(n);
> return 0;
> }
>
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