From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f180.google.com (mail-pf0-f180.google.com [209.85.192.180]) by kanga.kvack.org (Postfix) with ESMTP id 44EEA6B0256 for ; Thu, 28 Jan 2016 04:44:46 -0500 (EST) Received: by mail-pf0-f180.google.com with SMTP id o185so16331159pfb.1 for ; Thu, 28 Jan 2016 01:44:46 -0800 (PST) Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com. [202.81.31.142]) by mx.google.com with ESMTPS id x12si781998pfa.98.2016.01.28.01.44.44 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 28 Jan 2016 01:44:45 -0800 (PST) Received: from localhost by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 28 Jan 2016 19:44:37 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id DDEA42BB0054 for ; Thu, 28 Jan 2016 20:44:33 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u0S9iRqV12124372 for ; Thu, 28 Jan 2016 20:44:35 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u0S9i08l005912 for ; Thu, 28 Jan 2016 20:44:01 +1100 From: "Aneesh Kumar K.V" Subject: Re: [LSF/MM ATTEND] 2016: Requests to attend MM-summit In-Reply-To: References: <87k2n2usyf.fsf@linux.vnet.ibm.com> <20160122163801.GA16668@cmpxchg.org> Date: Thu, 28 Jan 2016 15:13:33 +0530 Message-ID: <877fiu59a2.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim , Johannes Weiner Cc: lsf-pc@lists.linux-foundation.org, Linux Memory Management List , Joonsoo Kim , Peter Zijlstra Joonsoo Kim writes: > Hello, > > 2016-01-23 1:38 GMT+09:00 Johannes Weiner : >> Hi, >> >> On Fri, Jan 22, 2016 at 10:11:12AM +0530, Aneesh Kumar K.V wrote: >>> * CMA allocator issues: >>> (1) order zero allocation failures: >>> We are observing order zero non-movable allocation failures in kernel >>> with CMA configured. We don't start a reclaim because our free memory check >>> does not consider free_cma. Hence the reclaim code assume we have enough free >>> pages. Joonsoo Kim tried to fix this with his ZOME_CMA patches. I would >>> like to discuss the challenges in getting this merged upstream. >>> https://lkml.org/lkml/2015/2/12/95 (ZONE_CMA) > > As far as I know, there is no disagreement on this patchset in last year LSF/MM. > Problem may be due to my laziness... Sorry about that. I will handle it soon. > Is there anything more that you concern? > >> The exclusion of cma pages from the watermark checks means that >> reclaim is happening too early, not too late, which leaves memory >> underutilized. That's what ZONE_CMA set out to fix. >> >> But unmovable allocations can still fail when the only free memory is >> inside CMA regions. I don't see how ZONE_CMA would fix that. >> >> CC Joonsoo > > I understand what Aneesh's problem is. > > Assume that > > X = non movable free page > Y = movable free page > Z = cma free page > > X < min watermark > X + Y > high watermark > Z > high watermark > > If there are bunch of consecutive movable allocation requests, > Y will decrease. After some time, Y will be exhausted. At that > time, there is enough Z so movable allocation request still can be > handled in fastpath and kswapd isn't waked up. In that situation, > if atomic non-movable page allocation for order-0 comes, > it would be failed. > > Although it isn't mentioned on ZONE_CMA patchset, it is also > fixed by that patchset because with that patchset, all CMA pages > are in CMA zone so freepage calculation is always precise. > That is the issue I am hitting and if we don't have any blocker against ZONE_CMA then we can drop this topic. -aneesh -- 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