From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id C04A76B004F for ; Wed, 9 Sep 2009 11:39:02 -0400 (EDT) Received: by vws6 with SMTP id 6so702076vws.12 for ; Wed, 09 Sep 2009 08:39:02 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20090909131945.0CF5.A69D9226@jp.fujitsu.com> References: <20090909131945.0CF5.A69D9226@jp.fujitsu.com> Date: Thu, 10 Sep 2009 00:39:02 +0900 Message-ID: <28c262360909090839j626ff818of930cf13a6185123@mail.gmail.com> Subject: Re: [rfc] lru_add_drain_all() vs isolation From: Minchan Kim Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Christoph Lameter , Peter Zijlstra , Mike Galbraith , Ingo Molnar , linux-mm , Oleg Nesterov , lkml List-ID: On Wed, Sep 9, 2009 at 1:27 PM, KOSAKI Motohiro wrote: >> The usefulness of a scheme like this requires: >> >> 1. There are cpus that continually execute user space code >> =A0 =A0without system interaction. >> >> 2. There are repeated VM activities that require page isolation / >> =A0 =A0migration. >> >> The first page isolation activity will then clear the lru caches of the >> processes doing number crunching in user space (and therefore the first >> isolation will still interrupt). The second and following isolation will >> then no longer interrupt the processes. >> >> 2. is rare. So the question is if the additional code in the LRU handlin= g >> can be justified. If lru handling is not time sensitive then yes. > > Christoph, I'd like to discuss a bit related (and almost unrelated) thing= . > I think page migration don't need lru_add_drain_all() as synchronous, bec= ause > page migration have 10 times retry. > > Then asynchronous lru_add_drain_all() cause > > =A0- if system isn't under heavy pressure, retry succussfull. > =A0- if system is under heavy pressure or RT-thread work busy busy loop, = retry failure. > > I don't think this is problematic bahavior. Also, mlock can use asynchrou= nous lru drain. I think, more exactly, we don't have to drain lru pages for mlocking. Mlocked pages will go into unevictable lru due to try_to_unmap when shrink of lru happens. How about removing draining in case of mlock? > > What do you think? > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. =A0For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > --=20 Kind regards, Minchan Kim -- 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