From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754092AbaEVInN (ORCPT ); Thu, 22 May 2014 04:43:13 -0400 Received: from cantor2.suse.de ([195.135.220.15]:34137 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754072AbaEVInL (ORCPT ); Thu, 22 May 2014 04:43:11 -0400 Message-ID: <537DB89B.8080301@suse.cz> Date: Thu, 22 May 2014 10:43:07 +0200 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: David Rientjes CC: Andrew Morton , Mel Gorman , Rik van Riel , Joonsoo Kim , Greg Thelen , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch -mm] mm, thp: avoid excessive compaction latency during fault fix References: <5371ED3F.6070505@suse.cz> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/22/2014 04:49 AM, David Rientjes wrote: > On Tue, 13 May 2014, Vlastimil Babka wrote: > >> I wonder what about a process doing e.g. mmap() with MAP_POPULATE. It seems to >> me that it would get only MIGRATE_ASYNC here, right? Since gfp_mask would >> include __GFP_NO_KSWAPD and it won't have PF_KTHREAD. >> I think that goes against the idea that with MAP_POPULATE you say you are >> willing to wait to have everything in place before you actually use the >> memory. So I guess you are also willing to wait for hugepages in that >> situation? >> > > I don't understand the distinction you're making between MAP_POPULATE and > simply a prefault of the anon memory. What is the difference in semantics > between using MAP_POPULATE and touching a byte every page size along the > range? In the latter, you'd be faulting thp with MIGRATE_ASYNC, so I > don't understand how MAP_POPULATE is any different or implies any > preference for hugepages. Hm, OK. It's right we cannot distinguish populating by touching the pages manually. Nevermind then. > -- > 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 >