From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table Date: Wed, 7 Nov 2007 13:13:18 +0100 Message-ID: <20071107121318.GB1817@ff.dom.local> References: <200711040018.15027.ak@suse.de> <20071103.162337.83099185.davem@davemloft.net> <472DAD90.4050709@cosmosbay.com> <20071107.024114.265595154.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dada1@cosmosbay.com, ak@suse.de, netdev@vger.kernel.org, acme@redhat.com To: David Miller Return-path: Received: from mx12.go2.pl ([193.17.41.142]:49113 "EHLO poczta.o2.pl" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750830AbXKGMJ2 (ORCPT ); Wed, 7 Nov 2007 07:09:28 -0500 Content-Disposition: inline In-Reply-To: <20071107.024114.265595154.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Nov 07, 2007 at 02:41:14AM -0800, David Miller wrote: > From: Eric Dumazet > Date: Sun, 04 Nov 2007 12:31:28 +0100 > > > [PATCH] INET : removes per bucket rwlock in tcp/dccp ehash table > > > > As done two years ago on IP route cache table (commit > > 22c047ccbc68fa8f3fa57f0e8f906479a062c426) , we can avoid using one lock per > > hash bucket for the huge TCP/DCCP hash tables. > > > > On a typical x86_64 platform, this saves about 2MB or 4MB of ram, for litle > > performance differences. (we hit a different cache line for the rwlock, but > > then the bucket cache line have a better sharing factor among cpus, since we > > dirty it less often). For netstat or ss commands that want a full scan of hash > > table, we perform fewer memory accesses. > > > > Using a 'small' table of hashed rwlocks should be more than enough to provide > > correct SMP concurrency between different buckets, without using too much > > memory. Sizing of this table depends on num_possible_cpus() and various CONFIG > > settings. > > > > This patch provides some locking abstraction that may ease a future work using > > a different model for TCP/DCCP table. > > > > Signed-off-by: Eric Dumazet > > Acked-by: Arnaldo Carvalho de Melo > > I'm going to push this current version to Linus, the space saving > really justify it and if we want to refine things further we do it > with followon work rather than blocking this patch. > > Thanks Eric! I hope my remarks didn't block anything?! I've written it's OK. So, I'm not sure it's useful or expected, but anyway: Acked-by: Jarek Poplawski Thanks, Jarek P.