From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 0E6286B0011 for ; Mon, 9 May 2011 21:41:38 -0400 (EDT) Date: Mon, 9 May 2011 18:48:06 -0700 From: Andrew Morton Subject: Re: [PATCH 1/4] VM/RMAP: Add infrastructure for batching the rmap chain locking Message-Id: <20110509184806.112bcebd.akpm@linux-foundation.org> In-Reply-To: <4DC89480.3060002@redhat.com> References: <1304623972-9159-1-git-send-email-andi@firstfloor.org> <1304623972-9159-2-git-send-email-andi@firstfloor.org> <20110509144324.8e79654a.akpm@linux-foundation.org> <4DC86947.30607@linux.intel.com> <20110509152841.ec957d23.akpm@linux-foundation.org> <20110509230255.GA6008@one.firstfloor.org> <20110509161622.57093622.akpm@linux-foundation.org> <20110510000517.GC6008@one.firstfloor.org> <20110509182656.5533628e.akpm@linux-foundation.org> <4DC89480.3060002@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Andi Kleen , Andi Kleen , linux-mm@kvack.org, Andrea Arcangeli , tim.c.chen@linux.intel.com, torvalds@linux-foundation.org, lwoodman@redhat.com, mel@csn.ul.ie On Mon, 09 May 2011 21:27:28 -0400 Rik van Riel wrote: > On 05/09/2011 09:26 PM, Andrew Morton wrote: > > On Tue, 10 May 2011 02:05:17 +0200 Andi Kleen wrote: > > > >>> hm, which atomic ops are those? We shouldn't need buslocked operations > >>> on UP. > >> > >> Good point. I forgot they're patched out. > >> > >> Then it's likely somewhat slower, but I doubt it's a significant > >> slowdown. Essentially it's just a few more if ()s > > > > And presumably some more instruction cachelines here and there. It'll > > be small, but 100*small == large. We can reduce the overhead to zero, > > it's a question of how ugly the end result is. > > More instruction cachelines, but fewer pointer dereferences > due to not looking up the lock all the time (if the root > anon_vma is the same). > Why would we be looking up a lock which doesn't exist? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org