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.
--
Michal Hocko
SUSE Labs
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