From: Shaohua Li Date: Thu, 11 Jun 2015 23:50:48 +0000 (-0700) Subject: net: don't wait for order-3 page allocation X-Git-Tag: v3.12.45~47 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=11d59bcaa8167d86b34b143e191e47c126ebea91;p=thirdparty%2Fkernel%2Fstable.git net: don't wait for order-3 page allocation [ Upstream commit fb05e7a89f500cfc06ae277bdc911b281928995d ] We saw excessive direct memory compaction triggered by skb_page_frag_refill. This causes performance issues and add latency. Commit 5640f7685831e0 introduces the order-3 allocation. According to the changelog, the order-3 allocation isn't a must-have but to improve performance. But direct memory compaction has high overhead. The benefit of order-3 allocation can't compensate the overhead of direct memory compaction. This patch makes the order-3 page allocation atomic. If there is no memory pressure and memory isn't fragmented, the alloction will still success, so we don't sacrifice the order-3 benefit here. If the atomic allocation fails, direct memory compaction will not be triggered, skb_page_frag_refill will fallback to order-0 immediately, hence the direct memory compaction overhead is avoided. In the allocation failure case, kswapd is waken up and doing compaction, so chances are allocation could success next time. alloc_skb_with_frags is the same. The mellanox driver does similar thing, if this is accepted, we must fix the driver too. V3: fix the same issue in alloc_skb_with_frags as pointed out by Eric V2: make the changelog clearer Cc: Eric Dumazet Cc: Chris Mason Cc: Debabrata Banerjee Signed-off-by: Shaohua Li Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- diff --git a/net/core/skbuff.c b/net/core/skbuff.c index fa8448a730a93..b01dd5f421dac 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -367,9 +367,11 @@ refill: for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) { gfp_t gfp = gfp_mask; - if (order) + if (order) { gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NOMEMALLOC; + gfp &= ~__GFP_WAIT; + } nc->frag.page = alloc_pages(gfp, order); if (likely(nc->frag.page)) break; diff --git a/net/core/sock.c b/net/core/sock.c index f9ec2f5be1c09..2335a7a130f28 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1907,8 +1907,10 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag) do { gfp_t gfp = sk->sk_allocation; - if (order) + if (order) { gfp |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY; + gfp &= ~__GFP_WAIT; + } pfrag->page = alloc_pages(gfp, order); if (likely(pfrag->page)) { pfrag->offset = 0;