On Mon, 2013-12-23 at 16:12 +0800, Jason Wang wrote:
> On 12/17/2013 08:16 AM, Michael Dalton wrote:
> > The virtio-net driver currently uses netdev_alloc_frag() for GFP_ATOMIC
> > mergeable rx buffer allocations. This commit migrates virtio-net to use
> > per-receive queue page frags for GFP_ATOMIC allocation. This change unifies
> > mergeable rx buffer memory allocation, which now will use skb_refill_frag()
> > for both atomic and GFP-WAIT buffer allocations.
> >
> > To address fragmentation concerns, if after buffer allocation there
> > is too little space left in the page frag to allocate a subsequent
> > buffer, the remaining space is added to the current allocated buffer
> > so that the remaining space can be used to store packet data.
> >
> > Signed-off-by: Michael Dalton <mwdalton@xxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 69 ++++++++++++++++++++++++++----------------------
> > 1 file changed, 38 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index c51a988..d38d130 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -78,6 +78,9 @@ struct receive_queue {
> > /* Chain pages by the private ptr. */
> > struct page *pages;
> >
> > + /* Page frag for GFP_ATOMIC packet buffer allocation. */
> > + struct page_frag atomic_frag;
> > +
> > /* RX: fragments + linear part + virtio header */
> > struct scatterlist sg[MAX_SKB_FRAGS + 2];
> >
> > @@ -127,9 +130,9 @@ struct virtnet_info {
> > struct mutex config_lock;
> >
> > /* Page_frag for GFP_KERNEL packet buffer allocation when we run
> > - * low on memory.
> > + * low on memory. May sleep.
> > */
> > - struct page_frag alloc_frag;
> > + struct page_frag sleep_frag;
>
> Any reason to use two different page_frag consider only
> skb_page_frag_refill() is used?
One is used under process context, where preemption and GFP_KERNEL are
allowed.
One is used from softirq context and GFP_ATOMIC. You cant share a common
page_frag.
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
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