From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f181.google.com (mail-ie0-f181.google.com [209.85.223.181]) by kanga.kvack.org (Postfix) with ESMTP id 2D15D6B0032 for ; Thu, 11 Jun 2015 18:53:07 -0400 (EDT) Received: by iebps5 with SMTP id ps5so13704498ieb.3 for ; Thu, 11 Jun 2015 15:53:07 -0700 (PDT) Received: from mail-ig0-x244.google.com (mail-ig0-x244.google.com. [2607:f8b0:4001:c05::244]) by mx.google.com with ESMTPS id a3si1838138icv.24.2015.06.11.15.53.06 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Jun 2015 15:53:06 -0700 (PDT) Received: by igdj8 with SMTP id j8so260047igd.0 for ; Thu, 11 Jun 2015 15:53:06 -0700 (PDT) Message-ID: <1434063184.27504.60.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [RFC v2] net: use atomic allocation for order-3 page allocation From: Eric Dumazet Date: Thu, 11 Jun 2015 15:53:04 -0700 In-Reply-To: <71a20cf185c485fa23d9347bd846a6f4e9753405.1434053941.git.shli@fb.com> References: <71a20cf185c485fa23d9347bd846a6f4e9753405.1434053941.git.shli@fb.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Shaohua Li Cc: netdev@vger.kernel.org, davem@davemloft.net, Kernel-team@fb.com, clm@fb.com, linux-mm@kvack.org, dbavatar@gmail.com, Eric Dumazet On Thu, 2015-06-11 at 15:27 -0700, Shaohua Li wrote: > 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. > > The mellanox driver does similar thing, if this is accepted, we must fix > the driver too. > > V2: make the changelog clearer > > Cc: Eric Dumazet > Signed-off-by: Shaohua Li > --- > net/core/sock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/core/sock.c b/net/core/sock.c > index 292f422..e9855a4 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -1883,7 +1883,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp) > > 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)) { OK, now what about alloc_skb_with_frags() ? This should have same problem right ? Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org