Kefeng reported that when run the follow test the mlock count in meminfo
cannot be decreased:
[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;
}
When __munlock_pagevec, we ClearPageMlock but isolation_failed in race
condition, and we do not count these page into delta_munlocked, which cause
mlock counter incorrect for we had Clear the PageMlock and cannot count down
the number in the feture.
Fix it by count the number of page whoes PageMlock flag is cleared.
Fixes: 1ebb7cc6a583 (" mm: munlock: batch NR_MLOCK zone state updates")
Signed-off-by: Yisheng Xie <xieyishe...@huawei.com>
Reported-by: Kefeng Wang <wangkefeng.w...@huawei.com>
Tested-by: Kefeng Wang <wangkefeng.w...@huawei.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Cc: Joern Engel <jo...@logfs.org>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Michel Lespinasse <wal...@google.com>
Cc: Hugh Dickins <hu...@google.com>
Cc: Rik van Riel <r...@redhat.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@suse.cz>
Cc: Xishi Qiu <qiuxi...@huawei.com>
CC: zhongjiang <zhongji...@huawei.com>
Cc: Hanjun Guo <guohan...@huawei.com>
Cc: <sta...@vger.kernel.org>
---
v2:
- use delta_munlocked for it doesn't do the increment in fastpath - 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
