Kefeng reported that when running the follow test, the mlock count in
meminfo will increases permanently:
[1] testcase
linux:~ # cat test_mlockal
grep Mlocked /proc/meminfo
for j in `seq 0 10`
do
for i in `seq 4 15`
do
./p_mlockall >> log &
done
sleep 0.2
done
# wait some time to let mlock counter decrease and 5s may not enough
sleep 5
grep Mlocked /proc/meminfo
linux:~ # cat p_mlockall.c
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#define SPACE_LEN 4096
int main(int argc, char ** argv)
{
int ret;
void *adr = malloc(SPACE_LEN);
if (!adr)
return -1;
ret = mlockall(MCL_CURRENT | MCL_FUTURE);
printf("mlcokall ret = %d\n", ret);
ret = munlockall();
printf("munlcokall ret = %d\n", ret);
free(adr);
return 0;
}
In __munlock_pagevec() we should decrement NR_MLOCK for each page where
we clear the PageMlocked flag. Commit 1ebb7cc6a583 ("mm: munlock: batch
NR_MLOCK zone state updates") has introduced a bug where we don't
decrement NR_MLOCK for pages where we clear the flag, but fail to
isolate them from the lru list (e.g. when the pages are on some other
cpu's percpu pagevec). Since PageMlocked stays cleared, the NR_MLOCK
accounting gets permanently disrupted by this.
Fix it by counting the number of page whoes PageMlock flag is cleared.
Fixes: 1ebb7cc6a583 ("mm: munlock: batch NR_MLOCK zone state updates")
Signed-off-by: Yisheng Xie <[email protected]>
Reported-by: Kefeng Wang <[email protected]>
Tested-by: Kefeng Wang <[email protected]>
Suggested-by: Vlastimil Babka <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Joern Engel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Xishi Qiu <[email protected]>
CC: zhongjiang <[email protected]>
Cc: Hanjun Guo <[email protected]>
Cc: <[email protected]>
---
v2:
- use delta_munlocked for it doesn't do the increment in fastpath - Vlastimil
v3:
- change the changelog to make it more clear - Vlastimil
Hi Andrew:
Could you please help to fold this?
Thanks
Yisheng Xie
mm/mlock.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/mlock.c b/mm/mlock.c
index c483c5c..b562b55 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -284,7 +284,7 @@ static void __munlock_pagevec(struct pagevec *pvec, struct
zone *zone)
{
int i;
int nr = pagevec_count(pvec);
- int delta_munlocked;
+ int delta_munlocked = -nr;
struct pagevec pvec_putback;
int pgrescued = 0;
@@ -304,6 +304,8 @@ static void __munlock_pagevec(struct pagevec *pvec, struct
zone *zone)
continue;
else
__munlock_isolation_failed(page);
+ } else {
+ delta_munlocked++;
}
/*
@@ -315,7 +317,6 @@ static void __munlock_pagevec(struct pagevec *pvec, struct
zone *zone)
pagevec_add(&pvec_putback, pvec->pages[i]);
pvec->pages[i] = NULL;
}
- delta_munlocked = -nr + pagevec_count(&pvec_putback);
__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
spin_unlock_irq(zone_lru_lock(zone));
--
1.7.12.4
