From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id B53EB6B0023 for ; Mon, 9 May 2011 21:28:06 -0400 (EDT) Message-ID: <4DC89480.3060002@redhat.com> Date: Mon, 09 May 2011 21:27:28 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/4] VM/RMAP: Add infrastructure for batching the rmap chain locking 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> In-Reply-To: <20110509182656.5533628e.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton 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 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). I suspect that will balance out pretty well. -- All rights reversed -- 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