From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ea0-f179.google.com (mail-ea0-f179.google.com [209.85.215.179]) by kanga.kvack.org (Postfix) with ESMTP id 742166B0031 for ; Wed, 15 Jan 2014 10:22:25 -0500 (EST) Received: by mail-ea0-f179.google.com with SMTP id r15so543394ead.38 for ; Wed, 15 Jan 2014 07:22:21 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n47si8272420eef.220.2014.01.15.07.22.21 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 15 Jan 2014 07:22:21 -0800 (PST) Date: Wed, 15 Jan 2014 15:22:18 +0000 From: Mel Gorman Subject: Re: [RFC] mm: show message when updating min_free_kbytes in thp Message-ID: <20140115152218.GL4963@suse.de> References: <20140103033303.GB4106@localhost.localdomain> <52C6FED2.7070700@intel.com> <20140105003501.GC4106@localhost.localdomain> <20140106164604.GC27602@dhcp22.suse.cz> <20140108101611.GD27937@dhcp22.suse.cz> <20140110081744.GC9437@dhcp22.suse.cz> <20140114200720.GM4106@localhost.localdomain> <20140114155241.7891fce1fb2b9dfdcde15a8c@linux-foundation.org> <20140114163533.ab191e118e82ca7b4d499551@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20140114163533.ab191e118e82ca7b4d499551@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: David Rientjes , Han Pingtian , linux-kernel@vger.kernel.org, Michal Hocko , linux-mm@kvack.org, Dave Hansen On Tue, Jan 14, 2014 at 04:35:33PM -0800, Andrew Morton wrote: > > Would it be overkill to save the kernel default both with and without thp > > and then doing a WARN_ON_ONCE() if a user-written value is ever less? > > Well, min_free_kbytes is a userspace thing, not a kernel thing - maybe > THP shouldn't be dinking with it. What effect is THP trying to achieve > and can we achieve it by other/better means? It moved logic from hugeadm where few people knew about it to the kernel. The value is related to anti-fragmentation. With the recommended setting the probability of mixing pages of different mobility within a single pageblock is reduced. Very very superficially, it reduces the number of instances the mm_page_alloc_extfrag tracepoint is triggered with parameters that are considered to be severely fragmenting. -- Mel Gorman SUSE Labs -- 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