From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751512AbdB1Fs1 (ORCPT ); Tue, 28 Feb 2017 00:48:27 -0500 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:49259 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751037AbdB1FsY (ORCPT ); Tue, 28 Feb 2017 00:48:24 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org Date: Tue, 28 Feb 2017 14:02:16 +0900 From: Minchan Kim To: Shaohua Li Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kernel-team@fb.com, mhocko@suse.com, hughd@google.com, hannes@cmpxchg.org, riel@redhat.com, mgorman@techsingularity.net, akpm@linux-foundation.org Subject: Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Message-ID: <20170228050216.GB2702@bbox> References: <14b8eb1d3f6bf6cc492833f183ac8c304e560484.1487965799.git.shli@fb.com> <20170227063315.GC23612@bbox> <20170227161907.GC62304@shli-mbp.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170227161907.GC62304@shli-mbp.local> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 27, 2017 at 08:19:08AM -0800, Shaohua Li wrote: > On Mon, Feb 27, 2017 at 03:33:15PM +0900, Minchan Kim wrote: > > Hi Shaohua, > > > > On Fri, Feb 24, 2017 at 01:31:47PM -0800, Shaohua Li wrote: > > > When memory pressure is high, we free MADV_FREE pages. If the pages are > > > not dirty in pte, the pages could be freed immediately. Otherwise we > > > can't reclaim them. We put the pages back to anonumous LRU list (by > > > setting SwapBacked flag) and the pages will be reclaimed in normal > > > swapout way. > > > > > > We use normal page reclaim policy. Since MADV_FREE pages are put into > > > inactive file list, such pages and inactive file pages are reclaimed > > > according to their age. This is expected, because we don't want to > > > reclaim too many MADV_FREE pages before used once pages. > > > > > > Based on Minchan's original patch > > > > > > Cc: Michal Hocko > > > Cc: Minchan Kim > > > Cc: Hugh Dickins > > > Cc: Johannes Weiner > > > Cc: Rik van Riel > > > Cc: Mel Gorman > > > Cc: Andrew Morton > > > Signed-off-by: Shaohua Li > > > --- > > > include/linux/rmap.h | 2 +- > > > mm/huge_memory.c | 2 ++ > > > mm/madvise.c | 1 + > > > mm/rmap.c | 40 +++++++++++++++++----------------------- > > > mm/vmscan.c | 34 ++++++++++++++++++++++------------ > > > 5 files changed, 43 insertions(+), 36 deletions(-) > > > > > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > > > index 7a39414..fee10d7 100644 > > > --- a/include/linux/rmap.h > > > +++ b/include/linux/rmap.h > > > @@ -298,6 +298,6 @@ static inline int page_mkclean(struct page *page) > > > #define SWAP_AGAIN 1 > > > #define SWAP_FAIL 2 > > > #define SWAP_MLOCK 3 > > > -#define SWAP_LZFREE 4 > > > +#define SWAP_DIRTY 4 > > > > I still don't convinced why we should introduce SWAP_DIRTY in try_to_unmap. > > https://marc.info/?l=linux-mm&m=148797879123238&w=2 > > > > We have been SetPageMlocked in there but why cannot we SetPageSwapBacked > > in there? It's not a thing to change LRU type but it's just indication > > we found the page's status changed in late. > > This one I don't have strong preference. Personally I agree with Johannes, > handling failure in vmscan sounds better. But since the failure handling is > just one statement, this probably doesn't make too much difference. If Johannes > and you made an agreement, I'll follow. I don't want to add unnecessary new return value(i.e., SWAP_DIRTY). If VM found lazyfree page dirty in try_to_unmap_one, it means "non-swappable page" so it's natural to set SetPageSwapBacked in there and return just SWAP_FAIL to activate it in vmscan.c. SWAP_FAIL means the page is non-swappable so it should be activated. I don't see any problem in there like software engineering pov. However, it seems everyone are happy with introdcuing SWAP_DIRTY so I don't insist on it which is not critical for this patchset. I looked over try_to_unmap and callers. Now, I think we could remove SWAP_MLOCK and maybe SWAP_AGAIN as well as SWAP_DIRTY that is to make try_to_unmap *bool*. So, it could be done by separate patchset. I will look into that in more. Acked-by: Minchan Kim Thanks.