From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751562AbeDFHIT (ORCPT ); Fri, 6 Apr 2018 03:08:19 -0400 Received: from mx2.suse.de ([195.135.220.15]:35323 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbeDFHIS (ORCPT ); Fri, 6 Apr 2018 03:08:18 -0400 Date: Fri, 6 Apr 2018 09:08:15 +0200 From: Michal Hocko To: Naoya Horiguchi Cc: "Kirill A. Shutemov" , Zi Yan , "linux-mm@kvack.org" , Andrew Morton , Vlastimil Babka , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] mm: shmem: enable thp migration (Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page) Message-ID: <20180406070815.GC8286@dhcp22.suse.cz> References: <20180403105411.hknofkbn6rzs26oz@node.shutemov.name> <20180405085927.GC6312@dhcp22.suse.cz> <20180405122838.6a6b35psizem4tcy@node.shutemov.name> <20180405124830.GJ6312@dhcp22.suse.cz> <20180405134045.7axuun6d7ufobzj4@node.shutemov.name> <20180405150547.GN6312@dhcp22.suse.cz> <20180405155551.wchleyaf4rxooj6m@node.shutemov.name> <20180405160317.GP6312@dhcp22.suse.cz> <20180406030706.GA2434@hori1.linux.bs1.fc.nec.co.jp> <20180406051452.GB23467@hori1.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180406051452.GB23467@hori1.linux.bs1.fc.nec.co.jp> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 06-04-18 05:14:53, Naoya Horiguchi wrote: > On Fri, Apr 06, 2018 at 03:07:11AM +0000, Horiguchi Naoya(堀口 直也) wrote: > ... > > ----- > > From e31ec037701d1cc76b26226e4b66d8c783d40889 Mon Sep 17 00:00:00 2001 > > From: Naoya Horiguchi > > Date: Fri, 6 Apr 2018 10:58:35 +0900 > > Subject: [PATCH] mm: enable thp migration for shmem thp > > > > My testing for the latest kernel supporting thp migration showed an > > infinite loop in offlining the memory block that is filled with shmem > > thps. We can get out of the loop with a signal, but kernel should > > return with failure in this case. > > > > What happens in the loop is that scan_movable_pages() repeats returning > > the same pfn without any progress. That's because page migration always > > fails for shmem thps. > > > > In memory offline code, memory blocks containing unmovable pages should > > be prevented from being offline targets by has_unmovable_pages() inside > > start_isolate_page_range(). So it's possible to change migratability > > for non-anonymous thps to avoid the issue, but it introduces more complex > > and thp-specific handling in migration code, so it might not good. > > > > So this patch is suggesting to fix the issue by enabling thp migration > > for shmem thp. Both of anon/shmem thp are migratable so we don't need > > precheck about the type of thps. > > > > Fixes: commit 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early") > > Signed-off-by: Naoya Horiguchi > > Cc: stable@vger.kernel.org # v4.15+ > > ... oh, I don't think this is suitable for stable. > Michal's fix in another email can come first with "CC: stable", > then this one. > Anyway I want to get some feedback on the change of this patch. My patch is indeed much simpler but it depends on [1] and that doesn't sound like a stable material as well because it depends on onether 2 patches. Maybe we need some other hack for 4.15 if we really care enough. [1] http://lkml.kernel.org/r/20180103082555.14592-4-mhocko@kernel.org -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id A60BA6B0003 for ; Fri, 6 Apr 2018 03:08:19 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id p189so142549pfp.1 for ; Fri, 06 Apr 2018 00:08:19 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id x9-v6si6487746pln.442.2018.04.06.00.08.18 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 06 Apr 2018 00:08:18 -0700 (PDT) Date: Fri, 6 Apr 2018 09:08:15 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: shmem: enable thp migration (Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page) Message-ID: <20180406070815.GC8286@dhcp22.suse.cz> References: <20180403105411.hknofkbn6rzs26oz@node.shutemov.name> <20180405085927.GC6312@dhcp22.suse.cz> <20180405122838.6a6b35psizem4tcy@node.shutemov.name> <20180405124830.GJ6312@dhcp22.suse.cz> <20180405134045.7axuun6d7ufobzj4@node.shutemov.name> <20180405150547.GN6312@dhcp22.suse.cz> <20180405155551.wchleyaf4rxooj6m@node.shutemov.name> <20180405160317.GP6312@dhcp22.suse.cz> <20180406030706.GA2434@hori1.linux.bs1.fc.nec.co.jp> <20180406051452.GB23467@hori1.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180406051452.GB23467@hori1.linux.bs1.fc.nec.co.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: "Kirill A. Shutemov" , Zi Yan , "linux-mm@kvack.org" , Andrew Morton , Vlastimil Babka , "linux-kernel@vger.kernel.org" On Fri 06-04-18 05:14:53, Naoya Horiguchi wrote: > On Fri, Apr 06, 2018 at 03:07:11AM +0000, Horiguchi Naoya(a ?a?GBP c?'a1?) wrote: > ... > > ----- > > From e31ec037701d1cc76b26226e4b66d8c783d40889 Mon Sep 17 00:00:00 2001 > > From: Naoya Horiguchi > > Date: Fri, 6 Apr 2018 10:58:35 +0900 > > Subject: [PATCH] mm: enable thp migration for shmem thp > > > > My testing for the latest kernel supporting thp migration showed an > > infinite loop in offlining the memory block that is filled with shmem > > thps. We can get out of the loop with a signal, but kernel should > > return with failure in this case. > > > > What happens in the loop is that scan_movable_pages() repeats returning > > the same pfn without any progress. That's because page migration always > > fails for shmem thps. > > > > In memory offline code, memory blocks containing unmovable pages should > > be prevented from being offline targets by has_unmovable_pages() inside > > start_isolate_page_range(). So it's possible to change migratability > > for non-anonymous thps to avoid the issue, but it introduces more complex > > and thp-specific handling in migration code, so it might not good. > > > > So this patch is suggesting to fix the issue by enabling thp migration > > for shmem thp. Both of anon/shmem thp are migratable so we don't need > > precheck about the type of thps. > > > > Fixes: commit 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early") > > Signed-off-by: Naoya Horiguchi > > Cc: stable@vger.kernel.org # v4.15+ > > ... oh, I don't think this is suitable for stable. > Michal's fix in another email can come first with "CC: stable", > then this one. > Anyway I want to get some feedback on the change of this patch. My patch is indeed much simpler but it depends on [1] and that doesn't sound like a stable material as well because it depends on onether 2 patches. Maybe we need some other hack for 4.15 if we really care enough. [1] http://lkml.kernel.org/r/20180103082555.14592-4-mhocko@kernel.org -- Michal Hocko SUSE Labs