Hi Kefeng, Could you please try this patch. Thanks Yisheng Xie ------------- >From a70ae975756e8e97a28d49117ab25684da631689 Mon Sep 17 00:00:00 2001 From: Yisheng Xie <xieyisheng1@xxxxxxxxxx> Date: Wed, 24 May 2017 16:01:24 +0800 Subject: [PATCH] mlock: fix mlock count can not decrease in race condition 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 sleep 5 # wait some time to let mlock decrease 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. Reported-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx> --- mm/mlock.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index c483c5c..71ba5cf 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 munlocked = 0; struct pagevec pvec_putback; int pgrescued = 0; @@ -296,6 +296,7 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) struct page *page = pvec->pages[i]; if (TestClearPageMlocked(page)) { + munlocked --; /* * We already have pin from follow_page_mask() * so we can spare the get_page() here. @@ -315,8 +316,8 @@ 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); + if (munlocked) + __mod_zone_page_state(zone, NR_MLOCK, munlocked); spin_unlock_irq(zone_lru_lock(zone)); /* Now we can release pins of pages that we are not munlocking */ -- 1.7.12.4 Thanks On 2017/5/23 22:41, Kefeng Wang wrote: > Hi All, > > Mlocked in meminfo will be increasing with an small testcase, and never be released in mainline, > here is a testcase[1] to reproduce the issue, but the centos7.2/7.3 will not increase. > > Is it normal? > > Thanks, > Kefeng > > > > > [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 > 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; > } > > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>