Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753636Ab1EFMOA (ORCPT ); Fri, 6 May 2011 08:14:00 -0400 Received: from anchor-post-1.mail.demon.net ([195.173.77.132]:50405 "EHLO anchor-post-1.mail.demon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751324Ab1EFMN7 (ORCPT ); Fri, 6 May 2011 08:13:59 -0400 Subject: Re: [PATCH] RCU: remove alignment padding from rcu_data on 64 bit builds From: Richard Kennedy To: Eric Dumazet Cc: "Paul E. McKenney" , lkml , Dipankar Sarma In-Reply-To: <1304662845.3131.23.camel@edumazet-laptop> References: <1304610604.1984.6.camel@castor.rsk> <1304662845.3131.23.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8" Date: Fri, 06 May 2011 13:13:56 +0100 Message-ID: <1304684036.1998.10.camel@castor.rsk> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 (2.32.2-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 912 Lines: 29 On Fri, 2011-05-06 at 08:20 +0200, Eric Dumazet wrote: ... > We could shrink this structure more, converting some 64bit fields to > 32bit ones. > > Rationale is the algo is working well on 32bit arches, no need to use > 64bit fields. > > candidates : completed, gpnum, passed_quiesc_completed, qlen, > qlen_last_fqs_check, blimit. > > Counters might be converted too. I don't know the code well enough to make that decision ;) Is it possible to shrink it enough to free up another cache line ? (16 longs to ints). CONFIG_NO_HZ adds 24 bytes so even for users with !CONFIG_NO_HZ the variables you suggest are not enough to free a cache line. regards Richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/