test_zswap uses hardcoded values of 4095 and 4096 throughout as page stride and page size, which are only correct on systems with a 4K page size. On architectures with larger pages (e.g., 64K on arm64 or ppc64), these constants cause memory to be touched at sub-page granularity, leading to inefficient access patterns and incorrect page count calculations, which can cause test failures.
Replace all hardcoded 4095 and 4096 values with a global pagesize variable initialized from sysconf(_SC_PAGESIZE) at startup, and remove the redundant local sysconf() calls scattered across individual functions. No functional change on 4K page size systems. Signed-off-by: Li Wang <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Michal Koutný <[email protected]> Cc: Muchun Song <[email protected]> Cc: Nhat Pham <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Shakeel Butt <[email protected]> Acked-by: Yosry Ahmed <[email protected]> --- tools/testing/selftests/cgroup/test_zswap.c | 45 ++++++++++++--------- 1 file changed, 25 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 37aa83c2f1b..23ff11390a3 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -15,6 +15,8 @@ #include "kselftest.h" #include "cgroup_util.h" +static int page_size; + #define PATH_ZSWAP "/sys/module/zswap" #define PATH_ZSWAP_ENABLED "/sys/module/zswap/parameters/enabled" @@ -73,11 +75,11 @@ static int allocate_and_read_bytes(const char *cgroup, void *arg) if (!mem) return -1; - for (int i = 0; i < size; i += 4095) + for (int i = 0; i < size; i += page_size) mem[i] = 'a'; /* Go through the allocated memory to (z)swap in and out pages */ - for (int i = 0; i < size; i += 4095) { + for (int i = 0; i < size; i += page_size) { if (mem[i] != 'a') ret = -1; } @@ -93,7 +95,7 @@ static int allocate_bytes(const char *cgroup, void *arg) if (!mem) return -1; - for (int i = 0; i < size; i += 4095) + for (int i = 0; i < size; i += page_size) mem[i] = 'a'; free(mem); return 0; @@ -167,7 +169,7 @@ static int test_swapin_nozswap(const char *root) int ret = KSFT_FAIL; char *test_group, mem_max_buf[32]; long swap_peak, zswpout, min_swap; - size_t allocation_size = sysconf(_SC_PAGESIZE) * 512; + size_t allocation_size = page_size * 512; min_swap = allocation_size / 4; snprintf(mem_max_buf, sizeof(mem_max_buf), "%zu", allocation_size * 3/4); @@ -245,7 +247,7 @@ static int test_zswapin(const char *root) goto out; } - if (zswpin < MB(24) / sysconf(_SC_PAGESIZE)) { + if (zswpin < MB(24) / page_size) { ksft_print_msg("at least 24MB should be brought back from zswap\n"); goto out; } @@ -272,9 +274,8 @@ static int test_zswapin(const char *root) */ static int attempt_writeback(const char *cgroup, void *arg) { - long pagesize = sysconf(_SC_PAGESIZE); size_t memsize = MB(4); - char buf[pagesize]; + char buf[page_size]; long zswap_usage; bool wb_enabled = *(bool *) arg; int ret = -1; @@ -289,11 +290,11 @@ static int attempt_writeback(const char *cgroup, void *arg) * half empty, this will result in data that is still compressible * and ends up in zswap, with material zswap usage. */ - for (int i = 0; i < pagesize; i++) - buf[i] = i < pagesize/2 ? (char) i : 0; + for (int i = 0; i < page_size; i++) + buf[i] = i < page_size/2 ? (char) i : 0; - for (int i = 0; i < memsize; i += pagesize) - memcpy(&mem[i], buf, pagesize); + for (int i = 0; i < memsize; i += page_size) + memcpy(&mem[i], buf, page_size); /* Try and reclaim allocated memory */ if (cg_write_numeric(cgroup, "memory.reclaim", memsize)) { @@ -304,8 +305,8 @@ static int attempt_writeback(const char *cgroup, void *arg) zswap_usage = cg_read_long(cgroup, "memory.zswap.current"); /* zswpin */ - for (int i = 0; i < memsize; i += pagesize) { - if (memcmp(&mem[i], buf, pagesize)) { + for (int i = 0; i < memsize; i += page_size) { + if (memcmp(&mem[i], buf, page_size)) { ksft_print_msg("invalid memory\n"); goto out; } @@ -441,7 +442,7 @@ static int test_no_invasive_cgroup_shrink(const char *root) if (cg_enter_current(control_group)) goto out; control_allocation = malloc(control_allocation_size); - for (int i = 0; i < control_allocation_size; i += 4095) + for (int i = 0; i < control_allocation_size; i += page_size) control_allocation[i] = 'a'; if (cg_read_key_long(control_group, "memory.stat", "zswapped") < 1) goto out; @@ -481,7 +482,7 @@ static int no_kmem_bypass_child(const char *cgroup, void *arg) values->child_allocated = true; return -1; } - for (long i = 0; i < values->target_alloc_bytes; i += 4095) + for (long i = 0; i < values->target_alloc_bytes; i += page_size) ((char *)allocation)[i] = 'a'; values->child_allocated = true; pause(); @@ -529,7 +530,7 @@ static int test_no_kmem_bypass(const char *root) min_free_kb_low = sys_info.totalram / 500000; values->target_alloc_bytes = (sys_info.totalram - min_free_kb_high * 1000) + sys_info.totalram * 5 / 100; - stored_pages_threshold = sys_info.totalram / 5 / 4096; + stored_pages_threshold = sys_info.totalram / 5 / page_size; trigger_allocation_size = sys_info.totalram / 20; /* Set up test memcg */ @@ -556,7 +557,7 @@ static int test_no_kmem_bypass(const char *root) if (!trigger_allocation) break; - for (int i = 0; i < trigger_allocation_size; i += 4095) + for (int i = 0; i < trigger_allocation_size; i += page_size) trigger_allocation[i] = 'b'; usleep(100000); free(trigger_allocation); @@ -567,8 +568,8 @@ static int test_no_kmem_bypass(const char *root) /* If memory was pushed to zswap, verify it belongs to memcg */ if (stored_pages > stored_pages_threshold) { int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped "); - int delta = stored_pages * 4096 - zswapped; - int result_ok = delta < stored_pages * 4096 / 4; + int delta = stored_pages * page_size - zswapped; + int result_ok = delta < stored_pages * page_size / 4; ret = result_ok ? KSFT_PASS : KSFT_FAIL; break; @@ -622,7 +623,7 @@ static int allocate_random_and_wait(const char *cgroup, void *arg) close(fd); /* Touch all pages to ensure they're faulted in */ - for (size_t i = 0; i < size; i += PAGE_SIZE) + for (size_t i = 0; i < size; i += page_size) mem[i] = mem[i]; /* Use MADV_PAGEOUT to push pages into zswap */ @@ -752,6 +753,10 @@ int main(int argc, char **argv) char root[PATH_MAX]; int i; + page_size = sysconf(_SC_PAGE_SIZE); + if (page_size <= 0) + page_size = BUF_SIZE; + ksft_print_header(); ksft_set_plan(ARRAY_SIZE(tests)); if (cg_find_unified_root(root, sizeof(root), NULL)) -- 2.53.0
