Re: [PATCH] net: use __GFP_NORETRY for high order allocations

From: David Rientjes
Date: Thu Feb 06 2014 - 16:03:22 EST


On Thu, 6 Feb 2014, Joe Perches wrote:

> On Thu, 2014-02-06 at 10:42 -0800, Eric Dumazet wrote:
> > sock_alloc_send_pskb() & sk_page_frag_refill()
> > have a loop trying high order allocations to prepare
> > skb with low number of fragments as this increases performance.
> >
> > Problem is that under memory pressure/fragmentation, this can
> > trigger OOM while the intent was only to try the high order
> > allocations, then fallback to order-0 allocations.
> []
> > Call Trace:
> > [<ffffffff8043766c>] dump_header+0xe1/0x23e
> > [<ffffffff80437a02>] oom_kill_process+0x6a/0x323
> > [<ffffffff80438443>] out_of_memory+0x4b3/0x50d
> > [<ffffffff8043a4a6>] __alloc_pages_may_oom+0xa2/0xc7
> > [<ffffffff80236f42>] __alloc_pages_nodemask+0x1002/0x17f0
> > [<ffffffff8024bd23>] alloc_pages_current+0x103/0x2b0
> > [<ffffffff8028567f>] sk_page_frag_refill+0x8f/0x160
> []
> > diff --git a/net/core/sock.c b/net/core/sock.c
> []
> > @@ -1775,7 +1775,9 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
> > while (order) {
> > if (npages >= 1 << order) {
> > page = alloc_pages(sk->sk_allocation |
> > - __GFP_COMP | __GFP_NOWARN,
> > + __GFP_COMP |
> > + __GFP_NOWARN |
> > + __GFP_NORETRY,
> > order);
> > if (page)
> > goto fill_page;
> > @@ -1845,7 +1847,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio)
> > gfp_t gfp = prio;
> >
> > if (order)
> > - gfp |= __GFP_COMP | __GFP_NOWARN;
> > + gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY;
>
> Perhaps add __GFP_THISNODE too ?
>

How does __GFP_THISNODE have anything to do with avoiding oom killing due
to high-order fragmentation? If they absolutely require local memory to
currnet's cpu node then that would make sense, but the fallback still
allocates order-0 memory remotely and with __GFP_THISNODE on this attempt
we wouldn't even attempt remote reclaim.
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