Messages in this thread | | | Date | Wed, 18 Jan 2023 15:26:08 +0100 | From | David Hildenbrand <> | Subject | Re: [PATCH v5 6/6] selftest: add testing unsharing and counting ksm zero page |
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On 30.12.22 02:18, yang.yang29@zte.com.cn wrote: > From: xu xin <xu.xin16@zte.com.cn> > > Add a function test_unmerge_zero_page() to test the functionality on > unsharing and counting ksm-placed zero pages and counting of this patch > series. > > test_unmerge_zero_page() actually contains three subjct test objects: > 1) whether the count of ksm zero page can react correctly to cow > (copy on write); > 2) whether the count of ksm zero page can react correctly to unmerge; > 3) whether ksm zero pages are really unmerged. > > Signed-off-by: xu xin <xu.xin16@zte.com.cn> > Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn> > Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> > Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> > > v4->v5: > fix error of "} while (end_scans < start_scans + 20);" to > "} while (end_scans < start_scans + 2);" in wait_two_full_scans(). > --- > tools/testing/selftests/vm/ksm_functional_tests.c | 103 +++++++++++++++++++++- > 1 file changed, 99 insertions(+), 4 deletions(-) > > diff --git a/tools/testing/selftests/vm/ksm_functional_tests.c b/tools/testing/selftests/vm/ksm_functional_tests.c > index b11b7e5115dc..b792798a54c4 100644 > --- a/tools/testing/selftests/vm/ksm_functional_tests.c > +++ b/tools/testing/selftests/vm/ksm_functional_tests.c > @@ -27,6 +27,8 @@ > > static int ksm_fd; > static int ksm_full_scans_fd; > +static int ksm_zero_pages_fd; > +static int ksm_use_zero_pages_fd;
If they are global, open them from main(), not from the test case.
> static int pagemap_fd; > static size_t pagesize; > > @@ -57,6 +59,22 @@ static bool range_maps_duplicates(char *addr, unsigned long size) > return false; > } > > +static bool check_ksm_zero_pages_count(unsigned long zero_size) > +{ > + unsigned long pages_expected = zero_size / (4 * KiB); > + char buf[20]; > + ssize_t read_size; > + unsigned long ksm_zero_pages; > + > + read_size = pread(ksm_zero_pages_fd, buf, sizeof(buf) - 1, 0); > + if (read_size < 0) > + return -errno; > + buf[read_size] = 0; > + ksm_zero_pages = strtol(buf, NULL, 10); > + > + return ksm_zero_pages == pages_expected;
Better call this function "ksm_get_zero_pages", do it similarly to ksm_get_full_scans() and do the comparison in the kernel.
> +} > + > static long ksm_get_full_scans(void) > { > char buf[10]; > @@ -70,15 +88,12 @@ static long ksm_get_full_scans(void) > return strtol(buf, NULL, 10); > } > > -static int ksm_merge(void) > +static int wait_two_full_scans(void) > { > long start_scans, end_scans; > > - /* Wait for two full scans such that any possible merging happened. */ > start_scans = ksm_get_full_scans(); > if (start_scans < 0) > - return start_scans; > - if (write(ksm_fd, "1", 1) != 1) > return -errno;
This change might not be required.
> do { > end_scans = ksm_get_full_scans(); > @@ -89,6 +104,34 @@ static int ksm_merge(void) > return 0; > } > > +static inline int ksm_merge(void) > +{ > + /* Wait for two full scans such that any possible merging happened. */ > + if (write(ksm_fd, "1", 1) != 1) > + return -errno; > + return wait_two_full_scans(); > +} > + > +static inline int make_cow(char *map, char val, unsigned long size) > +{ > + > + memset(map, val, size); > + return wait_two_full_scans();
Why is that required?
> +} > + > +static int unmerge_zero_page(char *start, unsigned long size) > +{ > + int ret; > + > + ret = madvise(start, size, MADV_UNMERGEABLE); > + if (ret) { > + ksft_test_result_fail("MADV_UNMERGEABLE failed\n"); > + return ret; > + } > + > + return wait_two_full_scans();
Dito, why is that required when unmerging?
> +} > + > static char *mmap_and_merge_range(char val, unsigned long size) > { > char *map; > @@ -146,6 +189,56 @@ static void test_unmerge(void) > munmap(map, size); > } > > +static void test_unmerge_zero_pages(void) > +{ > + const unsigned int size = 2 * MiB; > + char *map; > + > + ksft_print_msg("[RUN] %s\n", __func__); > + > + /* Confirm the interfaces*/ > + ksm_zero_pages_fd = open("/sys/kernel/mm/ksm/zero_pages_sharing", O_RDONLY); > + if (ksm_zero_pages_fd < 0) { > + ksft_test_result_skip("open(\"/sys/kernel/mm/ksm/zero_pages_sharing\") failed\n"); > + return; > + } > + ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR); > + if (ksm_use_zero_pages_fd < 0) { > + ksft_test_result_skip("open \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n"); > + return; > + } > + if (write(ksm_use_zero_pages_fd, "1", 1) != 1) { > + ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n"); > + return; > + } > + > + /* Mmap zero pages*/ > + map = mmap_and_merge_range(0x00, size);
Not checking for map == MAP_FAILED. Best to follow what test_unmerge() does.
> + > + /* Case 1: make Writing on ksm zero pages (COW) */ > + if (make_cow(map, 0xcf, size / 2)) { > + ksft_test_result_fail("COW failed\n"); > + goto unmap; > + } > + ksft_test_result(check_ksm_zero_pages_count(size / 2), > + "zero page count react to cow\n"); > +
Let's keep COW tests to cow.c and focus on explicit unmerging here. Once we add support for KSM in cow.c , we can also test that e.g., long-term R/O pinning works as expected. I have that on my todo list but would be pleasantly surprised if someone else could tackle it :)
> + /* Case 2: Call madvise(xxx, MADV_UNMERGEABLE)*/ > + if (unmerge_zero_page(map + size / 2, size / 4)) { > + ksft_test_result_fail("unmerge_zero_page failed\n"); > + goto unmap; > + }
Just avoid that helper and do it like test_unmerge(). Keep it simple.
> + ksft_test_result(check_ksm_zero_pages_count(size / 4), > + "zero page count react to unmerge\n"); > + > + /*Check if ksm pages are really unmerged */
Missing space at the beginning. + the comment is superfluous.
> + ksft_test_result(!range_maps_duplicates(map + size / 2, size / 4), > + "KSM zero pages were unmerged\n"); > + > +unmap: > + munmap(map, size); > +} > + > static void test_unmerge_discarded(void) > { > const unsigned int size = 2 * MiB; > @@ -261,11 +354,13 @@ int main(int argc, char **argv) > ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY); > if (ksm_full_scans_fd < 0) > ksft_exit_skip("open(\"/sys/kernel/mm/ksm/full_scans\") failed\n"); > +
Unrelated change.
> pagemap_fd = open("/proc/self/pagemap", O_RDONLY); > if (pagemap_fd < 0) > ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n"); > > test_unmerge(); > + test_unmerge_zero_pages(); > test_unmerge_discarded(); > #ifdef __NR_userfaultfd > test_unmerge_uffd_wp();
-- Thanks,
David / dhildenb
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