From: Jiayuan Chen <[email protected]> Add test_zswap_incompressible() to verify that the zswap_incomp memcg stat correctly tracks incompressible pages.
The test allocates memory filled with random data from /dev/urandom, which cannot be effectively compressed by zswap. When this data is swapped out to zswap, it should be stored as-is and tracked by the zswap_incomp counter. The test verifies that: 1. Pages are swapped out to zswap (zswpout increases) 2. Incompressible pages are tracked (zswap_incomp increases) test: dd if=/dev/zero of=/swapfile bs=1M count=2048 chmod 600 /swapfile mkswap /swapfile swapon /swapfile echo Y > /sys/module/zswap/parameters/enabled ./test_zswap TAP version 13 1..8 ok 1 test_zswap_usage ok 2 test_swapin_nozswap ok 3 test_zswapin ok 4 test_zswap_writeback_enabled ok 5 test_zswap_writeback_disabled ok 6 test_no_kmem_bypass ok 7 test_no_invasive_cgroup_shrink ok 8 test_zswap_incompressible Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0 Signed-off-by: Jiayuan Chen <[email protected]> --- tools/testing/selftests/cgroup/test_zswap.c | 96 +++++++++++++++++++++ 1 file changed, 96 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 64ebc3f3f203..8cb8a131357d 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -5,6 +5,7 @@ #include <unistd.h> #include <stdio.h> #include <signal.h> +#include <fcntl.h> #include <sys/sysinfo.h> #include <string.h> #include <sys/wait.h> @@ -574,6 +575,100 @@ static int test_no_kmem_bypass(const char *root) return ret; } +static int allocate_random_and_wait(const char *cgroup, void *arg) +{ + size_t size = (size_t)arg; + char *mem; + int fd; + ssize_t n; + + mem = malloc(size); + if (!mem) + return -1; + + /* Fill with random data from /dev/urandom - incompressible */ + fd = open("/dev/urandom", O_RDONLY); + if (fd < 0) { + free(mem); + return -1; + } + + for (size_t i = 0; i < size; ) { + n = read(fd, mem + i, size - i); + if (n <= 0) + break; + i += n; + } + close(fd); + + /* Touch all pages to ensure they're faulted in */ + for (size_t i = 0; i < size; i += 4096) + mem[i] = mem[i]; + + /* Keep memory alive for parent to reclaim and check stats */ + pause(); + free(mem); + return 0; +} + +static long get_zswap_incomp(const char *cgroup) +{ + return cg_read_key_long(cgroup, "memory.stat", "zswap_incomp "); +} + +/* + * Test that incompressible pages (random data) are tracked by zswap_incomp. + * + * Since incompressible pages stored in zswap are charged at full PAGE_SIZE + * (no memory savings), we cannot rely on memory.max pressure to push them + * into zswap. Instead, we allocate random data within memory.max, then use + * memory.reclaim to proactively push pages into zswap while checking the stat + * before the child exits (zswap_incomp is a gauge that decreases on free). + */ +static int test_zswap_incompressible(const char *root) +{ + int ret = KSFT_FAIL; + char *test_group; + long zswap_incomp; + pid_t child_pid; + int child_status; + + test_group = cg_name(root, "zswap_incompressible_test"); + if (!test_group) + goto out; + if (cg_create(test_group)) + goto out; + if (cg_write(test_group, "memory.max", "32M")) + goto out; + + child_pid = cg_run_nowait(test_group, allocate_random_and_wait, + (void *)MB(4)); + if (child_pid < 0) + goto out; + + /* Wait for child to finish allocating */ + usleep(500000); + + /* Proactively reclaim to push random pages into zswap */ + cg_write_numeric(test_group, "memory.reclaim", MB(4)); + + zswap_incomp = get_zswap_incomp(test_group); + if (zswap_incomp <= 0) { + ksft_print_msg("zswap_incomp not increased: %ld\n", zswap_incomp); + goto out_kill; + } + + ret = KSFT_PASS; + +out_kill: + kill(child_pid, SIGTERM); + waitpid(child_pid, &child_status, 0); +out: + cg_destroy(test_group); + free(test_group); + return ret; +} + #define T(x) { x, #x } struct zswap_test { int (*fn)(const char *root); @@ -586,6 +681,7 @@ struct zswap_test { T(test_zswap_writeback_disabled), T(test_no_kmem_bypass), T(test_no_invasive_cgroup_shrink), + T(test_zswap_incompressible), }; #undef T -- 2.43.0
