From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id E57CE6B004F for ; Thu, 25 Jun 2009 10:52:48 -0400 (EDT) Subject: Re: [PATCH] prevent to reclaim anon page of lumpy reclaim for no swap space From: Lee Schermerhorn In-Reply-To: <28c262360906250744h5bf9f0a0w265d8c35e7d69335@mail.gmail.com> References: <20090625183616.23b55b24.minchan.kim@barrios-desktop> <2f11576a0906250714o5d77db11wd32c1c7139753cb5@mail.gmail.com> <28c262360906250744h5bf9f0a0w265d8c35e7d69335@mail.gmail.com> Content-Type: text/plain Date: Thu, 25 Jun 2009 10:54:25 -0400 Message-Id: <1245941665.6459.18.camel@lts-notebook> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: KOSAKI Motohiro , Andrew Morton , Rik van Riel , KAMEZAWA Hiroyuki , linux-mm , lkml List-ID: On Thu, 2009-06-25 at 23:44 +0900, Minchan Kim wrote: > On Thu, Jun 25, 2009 at 11:14 PM, KOSAKI > Motohiro wrote: > >> This patch prevent to reclaim anon page in case of no swap space. > >> VM already prevent to reclaim anon page in various place. > >> But it doesnt't prevent it for lumpy reclaim. > >> > >> It shuffles lru list unnecessary so that it is pointless. > > > > NAK. > > > > 1. if system have no swap, add_to_swap() never get swap entry. > > eary check don't improve performance so much. > > Hmm. I mean no swap space but not no swap device. > add_to_swap ? You mean Rik pointed me out ? > If system have swap device, Rik's pointing is right. > I will update his suggestion. > > > 2. __isolate_lru_page() is not only called lumpy reclaim case, but > > also be called > > normal reclaim. > > You mean about performance degradation ? > I think most case have enough swap space and then one condition > variable(nr_swap_page) check is trivial. I think. > We can also use [un]likely but I am not sure it help us. > > > > 3. if system have no swap, anon pages shuffuling doesn't cause any matter. > > Again, I mean no swap space but no swap device system. > And I have a plan to remove anon_vma in no swap device system. > > As you point me out, it's pointless in no swap device system. > I don't like unnecessary structure memory footprint and locking overhead. > I think no swap device system is problem in server environment as well > as embedded. but I am not sure when I will do. :) > How will we walk the reverse map for try_to_unmap() for page migration or try_to_munlock() w/o anon_vma? Perhaps one can remove anon_vma when there is no swap device and migration and the unevictable lru are not configured--e.g., for embedded systems. Lee -- 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/ . Don't email: email@kvack.org