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SubjectRe: + mm-reclaim-madv_free-pages.patch added to -mm tree
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>

> ---
> 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.

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