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SubjectRe: [PATCH 10/17] netvm: Allow skb allocation to use PFMEMALLOC reserves
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On Thu, 2012-06-21 at 18:30 +0200, Sebastian Andrzej Siewior wrote:
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 1d6ecc8..9a58dcc 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -167,14 +206,19 @@ static void skb_under_panic(struct sk_buff *skb, int sz, void *here)
> > * %GFP_ATOMIC.
> > */
> > struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> > - int fclone, int node)
> > + int flags, int node)
> > {
> > struct kmem_cache *cache;
> > struct skb_shared_info *shinfo;
> > struct sk_buff *skb;
> > u8 *data;
> > + bool pfmemalloc;
> >
> > - cache = fclone ? skbuff_fclone_cache : skbuff_head_cache;
> > + cache = (flags & SKB_ALLOC_FCLONE)
> > + ? skbuff_fclone_cache : skbuff_head_cache;
> > +
> > + if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
> > + gfp_mask |= __GFP_MEMALLOC;
> >
> > /* Get the HEAD */
> > skb = kmem_cache_alloc_node(cache, gfp_mask & ~__GFP_DMA, node);
>
> This is mostly used by nic to refil their RX skb pool. You add the
> __GFP_MEMALLOC to the allocation to rise the change of a successfull refill
> for the swap case.
> A few drivers use build_skb() to create the skb. __netdev_alloc_skb()
> shouldn't be affected since the allocation happens with GFP_ATOMIC. Looking at
> TG3 it uses build_skb() and get_pages() / kmalloc(). Shouldn't this be some
> considered?

Please look at net-next, this was changed recently.

In fact most RX allocations are done using netdev_alloc_frag(), because
its called from __netdev_alloc_skb()

So tg3 is not anymore the exception, but the norm.





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