Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753915AbdCFP4T (ORCPT ); Mon, 6 Mar 2017 10:56:19 -0500 Received: from gum.cmpxchg.org ([85.214.110.215]:38776 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752968AbdCFP4O (ORCPT ); Mon, 6 Mar 2017 10:56:14 -0500 Date: Mon, 6 Mar 2017 10:49:06 -0500 From: Johannes Weiner To: Minchan Kim Cc: linux-kernel@vger.kernel.org, shli@fb.com, hillf.zj@alibaba-inc.com, hughd@google.com, mgorman@techsingularity.net, mhocko@suse.com, riel@redhat.com, mm-commits@vger.kernel.org Subject: Re: + mm-reclaim-madv_free-pages.patch added to -mm tree Message-ID: <20170306154906.GA2090@cmpxchg.org> References: <58b616a6.hCl1D/BVn0fPDi+K%akpm@linux-foundation.org> <20170303025237.GB3503@bbox> <20170303151851.GA16835@cmpxchg.org> <20170306030344.GG8779@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170306030344.GG8779@bbox> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6558 Lines: 171 On Mon, Mar 06, 2017 at 12:03:44PM +0900, Minchan Kim wrote: > On Fri, Mar 03, 2017 at 10:18:51AM -0500, Johannes Weiner wrote: > > On Fri, Mar 03, 2017 at 11:52:37AM +0900, Minchan Kim wrote: > > > On Tue, Feb 28, 2017 at 04:32:38PM -0800, akpm@linux-foundation.org wrote: > > > > > > > > The patch titled > > > > Subject: mm: reclaim MADV_FREE pages > > > > has been added to the -mm tree. Its filename is > > > > mm-reclaim-madv_free-pages.patch > > > > > > > > This patch should soon appear at > > > > http://ozlabs.org/~akpm/mmots/broken-out/mm-reclaim-madv_free-pages.patch > > > > and later at > > > > http://ozlabs.org/~akpm/mmotm/broken-out/mm-reclaim-madv_free-pages.patch > > > > > > > > Before you just go and hit "reply", please: > > > > a) Consider who else should be cc'ed > > > > b) Prefer to cc a suitable mailing list as well > > > > c) Ideally: find the original patch on the mailing list and do a > > > > reply-to-all to that, adding suitable additional cc's > > > > > > > > *** Remember to use Documentation/SubmitChecklist when testing your code *** > > > > > > > > The -mm tree is included into linux-next and is updated > > > > there every 3-4 working days > > > > > > > > ------------------------------------------------------ > > > > From: Shaohua Li > > > > Subject: mm: reclaim MADV_FREE pages > > > > > > > > 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 > > > > > > > > Link: http://lkml.kernel.org/r/14b8eb1d3f6bf6cc492833f183ac8c304e560484.1487965799.git.shli@fb.com > > > > Signed-off-by: Shaohua Li > > > > Acked-by: Minchan Kim > > > > Acked-by: Michal Hocko > > > > Acked-by: Johannes Weiner > > > > Acked-by: Hillf Danton > > > > Cc: Hugh Dickins > > > > Cc: Rik van Riel > > > > Cc: Mel Gorman > > > > Signed-off-by: Andrew Morton > > > > --- > > > > > > < snip > > > > > > > > @@ -1419,11 +1413,21 @@ static int try_to_unmap_one(struct page > > > > VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page), > > > > page); > > > > > > > > - if (!PageDirty(page)) { > > > > + /* > > > > + * swapin page could be clean, it has data stored in > > > > + * swap. We can't silently discard it without setting > > > > + * swap entry in the page table. > > > > + */ > > > > + if (!PageDirty(page) && !PageSwapCache(page)) { > > > > /* It's a freeable page by MADV_FREE */ > > > > dec_mm_counter(mm, MM_ANONPAGES); > > > > - rp->lazyfreed++; > > > > goto discard; > > > > + } else if (!PageSwapBacked(page)) { > > > > + /* dirty MADV_FREE page */ > > > > + set_pte_at(mm, address, pvmw.pte, pteval); > > > > + ret = SWAP_DIRTY; > > > > + page_vma_mapped_walk_done(&pvmw); > > > > + break; > > > > } > > > > > > There is no point to make this logic complicated with clean swapin-page. > > > > > > Andrew, > > > Could you fold below patch into the mm-reclaim-madv_free-pages.patch > > > if others are not against? > > > > > > Thanks. > > > > > > From 0c28f6560fbc4e65da4f4a8cc4664ab9f7b11cf3 Mon Sep 17 00:00:00 2001 > > > From: Minchan Kim > > > Date: Fri, 3 Mar 2017 11:42:52 +0900 > > > Subject: [PATCH] mm: clean up lazyfree page handling > > > > > > We can make it simple to understand without need to be aware of > > > clean-swapin page. > > > This patch just clean up lazyfree page handling in try_to_unmap_one. > > > > > > Signed-off-by: Minchan Kim > > > > Agreed, this is a litle easier to follow. > > > > Acked-by: Johannes Weiner > > Thanks, Johannes. > > > > > > --- > > > mm/rmap.c | 22 +++++++++++----------- > > > 1 file changed, 11 insertions(+), 11 deletions(-) > > > > > > diff --git a/mm/rmap.c b/mm/rmap.c > > > index bb45712..f7eab40 100644 > > > --- a/mm/rmap.c > > > +++ b/mm/rmap.c > > > @@ -1413,17 +1413,17 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > > > VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page), > > > page); > > > > Since you're removing the PageSwapCache() check and we're now assuming > > that !swapbacked is not in the swapcache, can you modify this to check > > PageSwapBacked(page) != PageSwapCache(page)? > > > > Better yet, change it into a warning and SWAP_FAIL. > > Maybe, what you wanted is > > !!PageSwapBacked(page) != !!PageSwapCache(page) Those testers return 0 or 1 ints, on x86 even bool. > Personally, I prefer && style rather than equation expression > in this case. > @@ -1413,20 +1413,24 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > * Store the swap location in the pte. > * See handle_pte_fault() ... > */ > - VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page), > - page); > + if (VM_WARN_ON_ONCE(PageSwapBacked(page) && > + !PageSwapCache(page))) { > + ret = SWAP_FAIL; But you're not adding the !swapbacked && swapcache case? > + page_vma_mapped_walk_done(&pvmw); > + break; > + } [...] > - /* > - * swapin page could be clean, it has data stored in > - * swap. We can't silently discard it without setting > - * swap entry in the page table. > - */ > - if (!PageDirty(page) && !PageSwapCache(page)) { > - /* It's a freeable page by MADV_FREE */ > - dec_mm_counter(mm, MM_ANONPAGES); > - goto discard; > - } else if (!PageSwapBacked(page)) { > - /* dirty MADV_FREE page */ > + /* MADV_FREE page check */ > + if (!PageSwapBacked(page)) { > + if (!PageDirty(page)) { > + dec_mm_counter(mm, MM_ANONPAGES); > + goto discard; > + } Andrew already has this, you might want to send the warning changes as a separate patch on top of this one.