From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43198 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933894AbbGHHgT (ORCPT ); Wed, 8 Jul 2015 03:36:19 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Chris Mason , Debabrata Banerjee , Shaohua Li , "David S. Miller" Subject: [PATCH 4.0 08/55] net: dont wait for order-3 page allocation Date: Wed, 8 Jul 2015 00:34:43 -0700 Message-Id: <20150708073239.309073420@linuxfoundation.org> In-Reply-To: <20150708073238.785749886@linuxfoundation.org> References: <20150708073238.785749886@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: stable-owner@vger.kernel.org List-ID: 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Shaohua Li [ 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: Greg Kroah-Hartman --- net/core/skbuff.c | 2 +- net/core/sock.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4443,7 +4443,7 @@ struct sk_buff *alloc_skb_with_frags(uns while (order) { if (npages >= 1 << order) { - page = alloc_pages(gfp_mask | + page = alloc_pages((gfp_mask & ~__GFP_WAIT) | __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY, --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1895,7 +1895,7 @@ bool skb_page_frag_refill(unsigned int s pfrag->offset = 0; if (SKB_FRAG_PAGE_ORDER) { - pfrag->page = alloc_pages(gfp | __GFP_COMP | + pfrag->page = alloc_pages((gfp & ~__GFP_WAIT) | __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY, SKB_FRAG_PAGE_ORDER); if (likely(pfrag->page)) {