From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757354AbcHWIig (ORCPT ); Tue, 23 Aug 2016 04:38:36 -0400 Received: from ud10.udmedia.de ([194.117.254.50]:45668 "EHLO mail.ud10.udmedia.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752944AbcHWIie (ORCPT ); Tue, 23 Aug 2016 04:38:34 -0400 Date: Tue, 23 Aug 2016 10:38:30 +0200 From: Markus Trippelsdorf To: Michal Hocko Cc: Andrew Morton , Mel Gorman , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [PATCH] mm: clarify COMPACTION Kconfig text Message-ID: <20160823083830.GC15849@x4> References: <1471939757-29789-1-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1471939757-29789-1-git-send-email-mhocko@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016.08.23 at 10:09 +0200, Michal Hocko wrote: > From: Michal Hocko > > The current wording of the COMPACTION Kconfig help text doesn't > emphasise that disabling COMPACTION might cripple the page allocator > which relies on the compaction quite heavily for high order requests and > an unexpected OOM can happen with the lack of compaction. Make sure > we are vocal about that. Just a few nitpicks inline below: > mm/Kconfig | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index 78a23c5c302d..0dff2f05b6d1 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -262,7 +262,14 @@ config COMPACTION > select MIGRATION > depends on MMU > help > - Allows the compaction of memory for the allocation of huge pages. > + Compaction is the only memory management component to form > + high order (larger physically contiguous) memory blocks > + reliably. Page allocator relies on the compaction heavily and The page allo... on compaction > + the lack of the feature can lead to unexpected OOM killer > + invocation for high order memory requests. You shouldnm't invocations shouldn't > + disable this option unless there is really a strong reason for really is > + it and then we are really interested to hear about that at would be -- Markus From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 01F986B0069 for ; Tue, 23 Aug 2016 04:38:33 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id e7so92189546lfe.0 for ; Tue, 23 Aug 2016 01:38:32 -0700 (PDT) Received: from mail.ud10.udmedia.de (ud10.udmedia.de. [194.117.254.50]) by mx.google.com with ESMTPS id fx15si2020625wjc.291.2016.08.23.01.38.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 23 Aug 2016 01:38:31 -0700 (PDT) Date: Tue, 23 Aug 2016 10:38:30 +0200 From: Markus Trippelsdorf Subject: Re: [PATCH] mm: clarify COMPACTION Kconfig text Message-ID: <20160823083830.GC15849@x4> References: <1471939757-29789-1-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1471939757-29789-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Mel Gorman , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org, LKML , Michal Hocko On 2016.08.23 at 10:09 +0200, Michal Hocko wrote: > From: Michal Hocko > > The current wording of the COMPACTION Kconfig help text doesn't > emphasise that disabling COMPACTION might cripple the page allocator > which relies on the compaction quite heavily for high order requests and > an unexpected OOM can happen with the lack of compaction. Make sure > we are vocal about that. Just a few nitpicks inline below: > mm/Kconfig | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index 78a23c5c302d..0dff2f05b6d1 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -262,7 +262,14 @@ config COMPACTION > select MIGRATION > depends on MMU > help > - Allows the compaction of memory for the allocation of huge pages. > + Compaction is the only memory management component to form > + high order (larger physically contiguous) memory blocks > + reliably. Page allocator relies on the compaction heavily and The page allo... on compaction > + the lack of the feature can lead to unexpected OOM killer > + invocation for high order memory requests. You shouldnm't invocations shouldn't > + disable this option unless there is really a strong reason for really is > + it and then we are really interested to hear about that at would be -- Markus -- 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