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SubjectRe: + mm-reclaim-madv_free-pages.patch added to -mm tree
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 <shli@fb.com>
> > > 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 <shli@fb.com>
> > > Acked-by: Minchan Kim <minchan@kernel.org>
> > > Acked-by: Michal Hocko <mhocko@suse.com>
> > > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > > Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
> > > Cc: Hugh Dickins <hughd@google.com>
> > > Cc: Rik van Riel <riel@redhat.com>
> > > Cc: Mel Gorman <mgorman@techsingularity.net>
> > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > ---
> >
> > < 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 <minchan@kernel.org>
> > 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 <minchan@kernel.org>
>
> Agreed, this is a litle easier to follow.
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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)

Personally, I prefer && style rather than equation expression
in this case.

How about this?
If others are not against, I will resend it to Andrew with
Acked|Reviewed-by all I got until now.

Thanks.

commit 118cfee42600
Author: Minchan Kim <minchan@kernel.org>
Date: Sat Mar 4 01:01:38 2017 +0000

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.

Link: http://lkml.kernel.org/r/20170303025237.GB3503@bbox
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Shaohua Li <shli@fb.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/rmap.c b/mm/rmap.c
index 3d86036d96ec..1377f7b0361e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -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;
+ 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;
+ }
+
+ /*
+ * If the page was redirtied, it cannot be
+ * discarded. Remap the page to page table.
+ */
set_pte_at(mm, address, pvmw.pte, pteval);
ret = SWAP_DIRTY;
page_vma_mapped_walk_done(&pvmw);
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