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Date:	Thu, 06 Feb 2014 10:42:42 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] net: use __GFP_NORETRY for high order allocations

From: Eric Dumazet <edumazet@...gle.com>

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.

We had various reports from unexpected regressions.

According to David, setting __GFP_NORETRY should be fine,
as the asynchronous compaction is still enabled, and this
will prevent OOM from kicking as in :

CFSClientEventm invoked oom-killer: gfp_mask=0x42d0, order=3, oom_adj=0,
oom_score_adj=0, oom_score_badness=2 (enabled),memcg_scoring=disabled
CFSClientEventm 

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
 [<ffffffff80295fa0>] tcp_sendmsg+0x560/0xee0
 [<ffffffff802a5037>] inet_sendmsg+0x67/0x100
 [<ffffffff80283c9c>] __sock_sendmsg_nosec+0x6c/0x90
 [<ffffffff80283e85>] sock_sendmsg+0xc5/0xf0
 [<ffffffff802847b6>] __sys_sendmsg+0x136/0x430
 [<ffffffff80284ec8>] sys_sendmsg+0x88/0x110
 [<ffffffff80711472>] system_call_fastpath+0x16/0x1b
Out of Memory: Kill process 2856 (bash) score 9999 or sacrifice child

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: David Rientjes <rientjes@...gle.com>
---
 net/core/sock.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 0c127dcdf6a8..5b6a9431b017 100644
--- 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;
 		pfrag->page = alloc_pages(gfp, order);
 		if (likely(pfrag->page)) {
 			pfrag->offset = 0;


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