From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: TCPBacklogDrops during aggressive bursts of traffic Date: Wed, 23 May 2012 10:10:36 -0700 Message-ID: <4FBD1A0C.4070606@intel.com> References: <1337092718.1689.45.camel@kjm-desktop.uk.level5networks.com> <1337099641.8512.1102.camel@edumazet-glaptop> <1337100454.2544.25.camel@bwh-desktop.uk.solarflarecom.com> <1337101280.8512.1108.camel@edumazet-glaptop> <1337272292.1681.16.camel@kjm-desktop.uk.level5networks.com> <1337272654.3403.20.camel@edumazet-glaptop> <1337674831.1698.7.camel@kjm-desktop.uk.level5networks.com> <1337678759.3361.147.camel@edumazet-glaptop> <1337679045.3361.154.camel@edumazet-glaptop> <1337699379.1698.30.camel@kjm-desktop.uk.level5networks.com> <1337703170.3361.217.camel@edumazet-glaptop> <1337704382.1698.53.camel@kjm-desktop.uk.level5networks.com> <1337705135.3361.226.camel@edumazet-glaptop> <1337720076.3361.667.camel@edumazet-glaptop> <1337766246.3361.2447.camel@edumazet-glaptop> <1 337774978.3361.2744.camel@edumazet-glaptop> <4FBD0A85.4040407@intel.com> <1337789530.3361.2992.camel@edumazet-glaptop> <1337791189.3361.3029.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Kieran Mansley , Jeff Kirsher , Ben Hutchings , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from mga11.intel.com ([192.55.52.93]:9755 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751145Ab2EWRKg (ORCPT ); Wed, 23 May 2012 13:10:36 -0400 In-Reply-To: <1337791189.3361.3029.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 05/23/2012 09:39 AM, Eric Dumazet wrote: > On Wed, 2012-05-23 at 18:12 +0200, Eric Dumazet wrote: > >> With current driver, a MTU=1500 frame uses : >> >> sk_buff (256 bytes) >> skb->head : 1024 bytes (or more exaclty now : 512 + 384) > By the way, NET_SKB_PAD adds 64 bytes so its 64 + 512 + 384 = 960 Actually pahole seems to be indicating to me the size of skb_shared_info is 320, unless something has changed in the last few days. When I get a chance I will try to remember to reduce the ixgbe header size to 256 which should also help. The only reason it is set to 512 was to deal with the fact that the old alloc_skb code wasn't aligning the shared info with the end of whatever size was allocated and so the 512 was an approximation to make better use of the 1K slab allocation back when we still were using hardware packet split. That should help to improve the page utilization for the headers since that would increase the uses of a page from 4 to 6 for the skb head frag, and it would drop truesize by another 256 bytes. Thanks, Alex