Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161228AbWBUAY7 (ORCPT ); Mon, 20 Feb 2006 19:24:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161227AbWBUAY7 (ORCPT ); Mon, 20 Feb 2006 19:24:59 -0500 Received: from smtp.osdl.org ([65.172.181.4]:34194 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1161228AbWBUAY6 (ORCPT ); Mon, 20 Feb 2006 19:24:58 -0500 Date: Mon, 20 Feb 2006 16:23:17 -0800 From: Andrew Morton To: Ravikiran G Thirumalai Cc: linux-kernel@vger.kernel.org, shai@scalex86.org Subject: Re: [patch] Cache align futex hash buckets Message-Id: <20060220162317.5c7b9778.akpm@osdl.org> In-Reply-To: <20060221000924.GD3594@localhost.localdomain> References: <20060220233242.GC3594@localhost.localdomain> <20060220153320.793b6a7d.akpm@osdl.org> <20060220153419.5ea8dd89.akpm@osdl.org> <20060221000924.GD3594@localhost.localdomain> X-Mailer: Sylpheed version 1.0.4 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1259 Lines: 33 Ravikiran G Thirumalai wrote: > > On Mon, Feb 20, 2006 at 03:34:19PM -0800, Andrew Morton wrote: > > Andrew Morton wrote: > > > > > > > @@ -100,9 +100,10 @@ struct futex_q { > > > > struct futex_hash_bucket { > > > > spinlock_t lock; > > > > struct list_head chain; > > > > -}; > > > > +} ____cacheline_internodealigned_in_smp; > > > > > > > > -static struct futex_hash_bucket futex_queues[1< > > > +static struct futex_hash_bucket futex_queues[1< > > > + __cacheline_aligned_in_smp; > > > > > > > > > > How much memory does that thing end up consuming? > > > > I think a megabyte? > > On most machines it would be 256 * 128 = 32k. or 16k on arches with 64B > cachelines. This looked like a simpler solution for spinlocks falling on > the same cacheline. So is 16/32k unreasonable? > CONFIG_X86_VSMP enables 4096-byte padding for ____cacheline_internodealigned_in_smp. It's a megabyte. - 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/