Re: [RFC PATCH] mm: fix mlock incorrent event account

[zhong jiang <zhongjiang@huawei.com>]

On 2017/5/25 22:19, Michal Hocko wrote:
> On Thu 25-05-17 21:48:56, zhong jiang wrote:
>> Hi Michal
>>
>> by a testcase, The patch is work as I think. The testcase is as follows.
>>
>> int main(void)
>> {
>>     char *map;
>>     int fd;
>>
>>     fd = open("test", O_CREAT|O_RDWR);
>>     unlink("test");
>>     ftruncate(fd, 4096);
>>     map = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE, fd, 0);
>>     map[0] = 11;
>>     mlock(map, sizeof(fd));
> just a nit
> you probably wanted mlock(map, 4096)
>
>>     ftruncate(fd, 0);
>>     close(fd);
>>     munlock(map, sizeof(fd));
> similarly here
>
>>     munmap(map, 4096);
>>
>>     return 0;
>> }
>>
>> before:
>> unevictable_pgs_mlocked 10589
>> unevictable_pgs_munlocked 10588
>> unevictable_pgs_cleared 1
>>
>> apply the patch;
>> after:
>> unevictable_pgs_mlocked 9497
>> unevictable_pgs_munlocked 9497
>> unevictable_pgs_cleared 1
> OK, this is definitely useful for the changelog.
>
>> unmap_mapping_range unmap them,  page_remove_rmap will deal with
>> clear_page_mlock situation.  we clear page Mlock flag and successful
>> isolate the page,  the page will putback the evictable list. but it is not
>> record the munlock event.
> and this as well. I haven't checked that but it gives reviewers chance
> to understand your thinking much better so it is definitely useful.
> Mlock code is everything but straightforward.
>
 HI, Michal

 I will add the above info the chanelog. and resent it in v2.

 Thanks
zhongjiang

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