From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH net-next 4/9] net: sctp: sctp_outq: consolidate chars into bitfield Date: Wed, 17 Apr 2013 11:26:21 +0200 Message-ID: <516E6ABD.2040904@redhat.com> References: <1366146438-8815-1-git-send-email-dborkman@redhat.com> <1366146438-8815-5-git-send-email-dborkman@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-sctp@vger.kernel.org To: David Laight Return-path: Received: from mx1.redhat.com ([209.132.183.28]:38361 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965826Ab3DQJ0k (ORCPT ); Wed, 17 Apr 2013 05:26:40 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 04/17/2013 10:43 AM, David Laight wrote: >> __u32 outstanding_bytes; >> >> - /* Are we doing fast-rtx on this queue */ >> - char fast_rtx; >> - >> - /* Corked? */ >> - char cork; >> - >> - /* Is this structure empty? */ >> - char empty; >> + __u8 fast_rtx:1, /* Are we doing fast-rtx on this queue */ >> + cork:1, /* Corked? */ >> + empty:1; /* Is this structure empty? */ >> }; > > Use of bitfields just makes the code slower. > The only real excuse for using them is to reduce the size > of a structure that is allocated a lot. sctp_outq is _embedded_ into an sctp_association structure, which has [size: 2280, cachelines: 36, members: 76]! A next step would be to try to reorder its elements carefully and see if we can reduce the size by filling some holes.