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Date: Thu, 3 Dec 2015 21:51:04 +0900
From: Minchan Kim <minchan@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Hugh Dickins <hughd@...gle.com>,
Johannes Weiner <hannes@...xchg.org>,
Rik van Riel <riel@...hat.com>, Jason Evans <je@...com>,
Daniel Micay <danielmicay@...il.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Shaohua Li <shli@...nel.org>, Michal Hocko <mhocko@...e.cz>,
yalin.wang2010@...il.com, Minchan Kim <minchan@...nel.org>
Subject: [PATCH] mm: account pglazyfreed exactly
If anon pages are zapped by unmapping between page_mapped check
and try_to_unmap in shrink_page_list, they could be !PG_dirty
although thre are not MADV_FREEed pages so that VM accoutns it
as pglazyfreed wrongly.
To fix, this patch counts the number of lazyfree ptes in
try_to_unmap_one and try_to_unmap returns SWAP_LZFREE only if
the count is not zero, page is !PG_dirty and SWAP_SUCCESS.
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
include/linux/rmap.h | 1 +
mm/rmap.c | 29 +++++++++++++++++++++++++----
mm/vmscan.c | 8 ++++++--
3 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 04d2aec64e57..bdf597c4f0be 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -312,5 +312,6 @@ static inline int page_mkclean(struct page *page)
#define SWAP_AGAIN 1
#define SWAP_FAIL 2
#define SWAP_MLOCK 3
+#define SWAP_LZFREE 4
#endif /* _LINUX_RMAP_H */
diff --git a/mm/rmap.c b/mm/rmap.c
index 321b633ee559..ffae0571c0ef 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1405,6 +1405,11 @@ void page_remove_rmap(struct page *page, bool compound)
*/
}
+struct rmap_private {
+ enum ttu_flags flags;
+ int lazyfreed;
+};
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -1416,7 +1421,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
pte_t pteval;
spinlock_t *ptl;
int ret = SWAP_AGAIN;
- enum ttu_flags flags = (enum ttu_flags)arg;
+ struct rmap_private *rp = arg;
+ enum ttu_flags flags = rp->flags;
/* munlock has nothing to gain from examining un-locked vmas */
if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
@@ -1512,6 +1518,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (!PageDirty(page) && (flags & TTU_LZFREE)) {
/* It's a freeable page by MADV_FREE */
dec_mm_counter(mm, MM_ANONPAGES);
+ rp->lazyfreed++;
goto discard;
}
@@ -1588,9 +1595,14 @@ static int page_not_mapped(struct page *page)
int try_to_unmap(struct page *page, enum ttu_flags flags)
{
int ret;
+ struct rmap_private rp = {
+ .flags = flags,
+ .lazyfreed = 0,
+ };
+
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
- .arg = (void *)flags,
+ .arg = (void *)&rp,
.done = page_not_mapped,
.anon_lock = page_lock_anon_vma_read,
};
@@ -1610,8 +1622,11 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
ret = rmap_walk(page, &rwc);
- if (ret != SWAP_MLOCK && !page_mapped(page))
+ if (ret != SWAP_MLOCK && !page_mapped(page)) {
ret = SWAP_SUCCESS;
+ if (rp.lazyfreed && !PageDirty(page))
+ ret = SWAP_LZFREE;
+ }
return ret;
}
@@ -1633,9 +1648,15 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
int try_to_munlock(struct page *page)
{
int ret;
+
+ struct rmap_private rp = {
+ .flags = TTU_MUNLOCK,
+ .lazyfreed = 0,
+ };
+
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
- .arg = (void *)TTU_MUNLOCK,
+ .arg = (void *)&rp,
.done = page_not_mapped,
.anon_lock = page_lock_anon_vma_read,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c2f69445190c..97788c9ce58c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -909,6 +909,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
enum page_references references = PAGEREF_RECLAIM_CLEAN;
bool dirty, writeback;
bool lazyfree = false;
+ int ret = SWAP_SUCCESS;
cond_resched();
@@ -1064,7 +1065,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* processes. Try to unmap it here.
*/
if (page_mapped(page) && mapping) {
- switch (try_to_unmap(page, lazyfree ?
+ switch (ret = try_to_unmap(page, lazyfree ?
(ttu_flags | TTU_BATCH_FLUSH | TTU_LZFREE) :
(ttu_flags | TTU_BATCH_FLUSH))) {
case SWAP_FAIL:
@@ -1073,6 +1074,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
goto keep_locked;
case SWAP_MLOCK:
goto cull_mlocked;
+ case SWAP_LZFREE:
+ goto lazyfree;
case SWAP_SUCCESS:
; /* try to free the page below */
}
@@ -1179,6 +1182,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
}
}
+lazyfree:
if (!mapping || !__remove_mapping(mapping, page, true))
goto keep_locked;
@@ -1191,7 +1195,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
*/
__ClearPageLocked(page);
free_it:
- if (lazyfree && !PageDirty(page))
+ if (ret == SWAP_LZFREE)
count_vm_event(PGLAZYFREED);
nr_reclaimed++;
--
1.9.1
--
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