From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next v3] net: use a per task frag allocator Date: Mon, 24 Sep 2012 16:39:46 -0400 (EDT) Message-ID: <20120924.163946.1641999339438679497.davem@davemloft.net> References: <1348261871.2669.962.camel@edumazet-glaptop> <1348477482.26828.235.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: subramanian.vijay@gmail.com, netdev@vger.kernel.org, bhutchings@solarflare.com, alexander.h.duyck@intel.com To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:54277 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932230Ab2IXUjt (ORCPT ); Mon, 24 Sep 2012 16:39:49 -0400 In-Reply-To: <1348477482.26828.235.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Mon, 24 Sep 2012 11:04:42 +0200 > From: Eric Dumazet > > We currently use a per socket order-0 page cache for tcp_sendmsg() > operations. > > This page is used to build fragments for skbs. > > Its done to increase probability of coalescing small write() into > single segments in skbs still in write queue (not yet sent) > > But it wastes a lot of memory for applications handling many mostly > idle sockets, since each socket holds one page in sk->sk_sndmsg_page > > Its also quite inefficient to build TSO 64KB packets, because we need > about 16 pages per skb on arches where PAGE_SIZE = 4096, so we hit > page allocator more than wanted. > > This patch adds a per task frag allocator and uses bigger pages, > if available. An automatic fallback is done in case of memory pressure. > > (up to 32768 bytes per frag, thats order-3 pages on x86) > > This increases TCP stream performance by 20% on loopback device, > but also benefits on other network devices, since 8x less frags are > mapped on transmit and unmapped on tx completion. Alexander Duyck > mentioned a probable performance win on systems with IOMMU enabled. > > Its possible some SG enabled hardware cant cope with bigger fragments, > but their ndo_start_xmit() should already handle this, splitting a > fragment in sub fragments, since some arches have PAGE_SIZE=65536 > > Successfully tested on various ethernet devices. > (ixgbe, igb, bnx2x, tg3, mellanox mlx4) > > Signed-off-by: Eric Dumazet I'm going to apply this, nice work Eric. I'll also take care of the trailing whitespace pointed out by others. Thanks again.