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

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>
---
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);

- /*
- * 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);
--
2.7.4
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