Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932512AbWBVBuu (ORCPT ); Tue, 21 Feb 2006 20:50:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932514AbWBVBuu (ORCPT ); Tue, 21 Feb 2006 20:50:50 -0500 Received: from smtp101.mail.mud.yahoo.com ([209.191.85.211]:46504 "HELO smtp101.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S932512AbWBVBuu (ORCPT ); Tue, 21 Feb 2006 20:50:50 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=ARzBEcvw6vpQlEhxpiPZn11Kkff3z63ERg6nLGAx7BetWY5PKtJpZf2+5lw652nvGzRyx03vsPkDOmtgX+DrxC+0evzsl/GUDH17Yzti7ulrrl37+PbY85BWhitis14svHdCBGKeG8RgPV6kmOOnGv+0LeXBfgXJURgeaWKqSno= ; Message-ID: <43FBB2E8.2020300@yahoo.com.au> Date: Wed, 22 Feb 2006 11:40:08 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Christoph Lameter CC: Ravikiran G Thirumalai , Andrew Morton , linux-kernel@vger.kernel.org, "Shai Fultheim (Shai@scalex86.org)" Subject: Re: [patch] Cache align futex hash buckets References: <20060220233242.GC3594@localhost.localdomain> <43FA8938.70006@yahoo.com.au> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1074 Lines: 31 Christoph Lameter wrote: > On Tue, 21 Feb 2006, Nick Piggin wrote: > > >>Ravikiran G Thirumalai wrote: >> >>>Following change places each element of the futex_queues hashtable on a >>>different cacheline. Spinlocks of adjacent hash buckets lie on the same >>>cacheline otherwise. >>> >> >>It does not make sense to add swaths of unused memory into a hashtable for >>this purpose, does it? > > > It does if you essentially have a 4k cacheline (because you are doing NUMA > in software with multiple PCs....) and transferring control of that > cacheline is comparatively expensive. > Instead of 1MB hash with 256 entries in it covering 256 cachelines, you have a 1MB hash with 65536(ish) entries covering 256 cachelines. - SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/