Re: [PATCH v2] mlock: fix mlock count can not decrease in race condition
Hi Vlastimil,
Thanks for comment!
On 2017/5/25 14:32, Vlastimil Babka wrote:
> On 05/25/2017 04:13 AM, Yisheng Xie wrote:
>> Kefeng reported that when run the follow test the mlock count
>
>> in meminfo
>> cannot be decreased:
>
> "increases permanently."?
Yes if I am not mis-understanding what your means.
>
>> [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
>> #include
>> #include
>>
>> #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.
>
> Can I suggest the following instead:
>
> 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.
That's much better and clear. Should I send another version ?
Thanks
Yisheng Xie
>
>> 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
>> Reported-by: Kefeng Wang
>> Tested-by: Kefeng Wang
>> Cc: Vlastimil Babka
>
> Acked-by: Vlastimil Babka
>
> Thanks!
>
>> Cc: Joern Engel
>> Cc: Mel Gorman
>> Cc: Michel Lespinasse
>> Cc: Hugh Dickins
>> Cc: Rik van Riel
>> Cc: Johannes Weiner
>> Cc: Michal Hocko
>> Cc: Xishi Qiu
>> CC: zhongjiang
>> Cc: Hanjun Guo
>> Cc:
>> ---
>> 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(_putback, pvec->pages[i]);
>> pvec->pages[i] = NULL;
>> }
>> -delta_munlocked = -nr + pagevec_count(_putback);
>> __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
>> spin_unlock_irq(zone_lru_lock(zone));
>>
>>
>
>
> .
>
Re: [PATCH v2] mlock: fix mlock count can not decrease in race condition
Hi Vlastimil,
Thanks for comment!
On 2017/5/25 14:32, Vlastimil Babka wrote:
> On 05/25/2017 04:13 AM, Yisheng Xie wrote:
>> Kefeng reported that when run the follow test the mlock count
>
>> in meminfo
>> cannot be decreased:
>
> "increases permanently."?
Yes if I am not mis-understanding what your means.
>
>> [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
>> #include
>> #include
>>
>> #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.
>
> Can I suggest the following instead:
>
> 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.
That's much better and clear. Should I send another version ?
Thanks
Yisheng Xie
>
>> 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
>> Reported-by: Kefeng Wang
>> Tested-by: Kefeng Wang
>> Cc: Vlastimil Babka
>
> Acked-by: Vlastimil Babka
>
> Thanks!
>
>> Cc: Joern Engel
>> Cc: Mel Gorman
>> Cc: Michel Lespinasse
>> Cc: Hugh Dickins
>> Cc: Rik van Riel
>> Cc: Johannes Weiner
>> Cc: Michal Hocko
>> Cc: Xishi Qiu
>> CC: zhongjiang
>> Cc: Hanjun Guo
>> Cc:
>> ---
>> 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(_putback, pvec->pages[i]);
>> pvec->pages[i] = NULL;
>> }
>> -delta_munlocked = -nr + pagevec_count(_putback);
>> __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
>> spin_unlock_irq(zone_lru_lock(zone));
>>
>>
>
>
> .
>
Re: [PATCH v2] mlock: fix mlock count can not decrease in race condition
On 05/25/2017 04:13 AM, Yisheng Xie wrote:
> Kefeng reported that when run the follow test the mlock count
> in meminfo
> cannot be decreased:
"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
> #include
> #include
>
> #define SPACE_LEN4096
>
> 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.
Can I suggest the following instead:
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 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
> Reported-by: Kefeng Wang
> Tested-by: Kefeng Wang
> Cc: Vlastimil Babka
Acked-by: Vlastimil Babka
Thanks!
> Cc: Joern Engel
> Cc: Mel Gorman
> Cc: Michel Lespinasse
> Cc: Hugh Dickins
> Cc: Rik van Riel
> Cc: Johannes Weiner
> Cc: Michal Hocko
> Cc: Xishi Qiu
> CC: zhongjiang
> Cc: Hanjun Guo
> Cc:
> ---
> 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(_putback, pvec->pages[i]);
> pvec->pages[i] = NULL;
> }
> - delta_munlocked = -nr + pagevec_count(_putback);
> __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
> spin_unlock_irq(zone_lru_lock(zone));
>
>
Re: [PATCH v2] mlock: fix mlock count can not decrease in race condition
On 05/25/2017 04:13 AM, Yisheng Xie wrote:
> Kefeng reported that when run the follow test the mlock count
> in meminfo
> cannot be decreased:
"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
> #include
> #include
>
> #define SPACE_LEN4096
>
> 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.
Can I suggest the following instead:
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 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
> Reported-by: Kefeng Wang
> Tested-by: Kefeng Wang
> Cc: Vlastimil Babka
Acked-by: Vlastimil Babka
Thanks!
> Cc: Joern Engel
> Cc: Mel Gorman
> Cc: Michel Lespinasse
> Cc: Hugh Dickins
> Cc: Rik van Riel
> Cc: Johannes Weiner
> Cc: Michal Hocko
> Cc: Xishi Qiu
> CC: zhongjiang
> Cc: Hanjun Guo
> Cc:
> ---
> 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(_putback, pvec->pages[i]);
> pvec->pages[i] = NULL;
> }
> - delta_munlocked = -nr + pagevec_count(_putback);
> __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
> spin_unlock_irq(zone_lru_lock(zone));
>
>
[PATCH v2] 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
# 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
#include
#include
#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
Reported-by: Kefeng Wang
Tested-by: Kefeng Wang
Cc: Vlastimil Babka
Cc: Joern Engel
Cc: Mel Gorman
Cc: Michel Lespinasse
Cc: Hugh Dickins
Cc: Rik van Riel
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Xishi Qiu
CC: zhongjiang
Cc: Hanjun Guo
Cc:
---
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(_putback, pvec->pages[i]);
pvec->pages[i] = NULL;
}
- delta_munlocked = -nr + pagevec_count(_putback);
__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
spin_unlock_irq(zone_lru_lock(zone));
--
1.7.12.4
[PATCH v2] 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
# 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
#include
#include
#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
Reported-by: Kefeng Wang
Tested-by: Kefeng Wang
Cc: Vlastimil Babka
Cc: Joern Engel
Cc: Mel Gorman
Cc: Michel Lespinasse
Cc: Hugh Dickins
Cc: Rik van Riel
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Xishi Qiu
CC: zhongjiang
Cc: Hanjun Guo
Cc:
---
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(_putback, pvec->pages[i]);
pvec->pages[i] = NULL;
}
- delta_munlocked = -nr + pagevec_count(_putback);
__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
spin_unlock_irq(zone_lru_lock(zone));
--
1.7.12.4
