From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id E88018D003A for ; Mon, 14 Mar 2011 22:47:29 -0400 (EDT) Date: Mon, 14 Mar 2011 19:44:21 -0700 From: Andrew Morton Subject: Re: [PATCH 2/2 v4]mm: batch activate_page() to reduce lock contention Message-Id: <20110314194421.6474cfc5.akpm@linux-foundation.org> In-Reply-To: References: <1299735019.2337.63.camel@sli10-conroe> <20110314144540.GC11699@barrios-desktop> <1300154014.2337.74.camel@sli10-conroe> <20110314192834.8ffeda55.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Shaohua Li , linux-mm , Andi Kleen , KOSAKI Motohiro , Rik van Riel , mel , Johannes Weiner On Tue, 15 Mar 2011 11:40:46 +0900 Minchan Kim wrote: > On Tue, Mar 15, 2011 at 11:28 AM, Andrew Morton > wrote: > > On Tue, 15 Mar 2011 11:12:37 +0900 Minchan Kim wrote: > > > >> >> I can't understand why we should hanlde activate_page_pvecs specially. > >> >> Please, enlighten me. > >> > Not it's special. akpm asked me to do it this time. Reducing little > >> > memory is still worthy anyway, so that's it. We can do it for other > >> > pvecs too, in separate patch. > >> > >> Understandable but I don't like code separation by CONFIG_SMP for just > >> little bit enhance of memory usage. In future, whenever we use percpu, > >> do we have to implement each functions for both SMP and non-SMP? > >> Is it desirable? > >> Andrew, Is it really valuable? > > > > It's a little saving of text footprint. __It's also probably faster this way - > > putting all the pages into a pagevec then later processing them won't > > be very L1 cache friendly. > > > > > > I am not sure how much effective it is in UP. But if L1 cache friendly > is important concern, we should not use per-cpu about hot operation. It's not due to the percpu thing. The issue is putting 14 pages into a pagevec and then later processing them after the older ones might have fallen out of cache. > I think more important thing in embedded (normal UP), it is a lock latency. > I don't want to hold/release the lock per page. There is no lock on UP builds. -- 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