On Mon, Feb 05, 2024 at 02:56:08PM -0800, Nhat Pham wrote: > Add a selftest to cover the zswapin code path, allocating more memory > than the cgroup limit to trigger swapout/zswapout, then reading the > pages back in memory several times. This is inspired by a recently > encountered kernel crash on the zswapin path in our internal kernel, > which went undetected because of a lack of test coverage for this path. > > Add a selftest to verify that when memory.zswap.max = 0, no pages can go > to the zswap pool for the cgroup. > > Suggested-by: Rik van Riel <[email protected]> > Suggested-by: Yosry Ahmed <[email protected]> > Signed-off-by: Nhat Pham <[email protected]>
LGTM with a few nits below: Acked-by: Yosry Ahmed <[email protected]> Thanks! > --- > tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++- > 1 file changed, 119 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/cgroup/test_zswap.c > b/tools/testing/selftests/cgroup/test_zswap.c > index 32ce975b21d1..c263610a4a60 100644 > --- a/tools/testing/selftests/cgroup/test_zswap.c > +++ b/tools/testing/selftests/cgroup/test_zswap.c > @@ -60,6 +60,27 @@ static long get_zswpout(const char *cgroup) > return cg_read_key_long(cgroup, "memory.stat", "zswpout "); > } > > +static int allocate_and_read_bytes(const char *cgroup, void *arg) > +{ > + size_t size = (size_t)arg; > + char *mem = (char *)malloc(size); > + int ret = 0; > + > + if (!mem) > + return -1; > + for (int i = 0; i < size; i += 4095) > + mem[i] = 'a'; > + > + /* go through the allocated memory to (z)swap in and out pages */ nit: s/go/Go > + for (int i = 0; i < size; i += 4095) { > + if (mem[i] != 'a') > + ret = -1; > + } > + > + free(mem); > + return ret; > +} > + > static int allocate_bytes(const char *cgroup, void *arg) > { > size_t size = (size_t)arg; > @@ -100,7 +121,6 @@ static int test_zswap_usage(const char *root) > int ret = KSFT_FAIL; > char *test_group; > > - /* Set up */ We removed this comment here. > test_group = cg_name(root, "no_shrink_test"); > if (!test_group) > goto out; > @@ -133,6 +153,102 @@ static int test_zswap_usage(const char *root) > return ret; > } > > +/* > + * Check that when memory.zswap.max = 0, no pages can go to the zswap pool > for > + * the cgroup. > + */ > +static int test_swapin_nozswap(const char *root) > +{ > + int ret = KSFT_FAIL; > + char *test_group; > + long swap_peak, zswpout; > + > + test_group = cg_name(root, "no_zswap_test"); > + if (!test_group) > + goto out; > + if (cg_create(test_group)) > + goto out; > + if (cg_write(test_group, "memory.max", "8M")) > + goto out; > + if (cg_write(test_group, "memory.zswap.max", "0")) > + goto out; > + > + /* Allocate and read more than memory.max to trigger swapin */ > + if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32))) > + goto out; > + > + /* Verify that pages are swapped out, but no zswap happened */ > + swap_peak = cg_read_long(test_group, "memory.swap.peak"); > + if (swap_peak < 0) { > + ksft_print_msg("failed to get cgroup's swap_peak\n"); > + goto out; > + } > + > + if (swap_peak == 0) { > + ksft_print_msg("pages should be swapped out\n"); > + goto out; > + } We can actually check that this number is >= 24M instead. Not a big deal, but might as well. > + > + zswpout = get_zswpout(test_group); > + if (zswpout < 0) { > + ksft_print_msg("failed to get zswpout\n"); > + goto out; > + } > + > + if (zswpout > 0) { > + ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n"); > + goto out; > + } > + > + ret = KSFT_PASS; > + > +out: > + cg_destroy(test_group); > + free(test_group); > + return ret; > +} > + > +/* Simple test to verify the (z)swapin code paths */ > +static int test_zswapin(const char *root) > +{ > + int ret = KSFT_FAIL; > + char *test_group; > + long zswpin; > + > + /* Set up */ Yet we added a similar one here :) > + test_group = cg_name(root, "zswapin_test"); > + if (!test_group) > + goto out; > + if (cg_create(test_group)) > + goto out; > + if (cg_write(test_group, "memory.max", "8M")) > + goto out; > + if (cg_write(test_group, "memory.zswap.max", "max")) > + goto out; > + > + /* Allocate and read more than memory.max to trigger (z)swap in */ > + if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32))) > + goto out; > + > + zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin "); > + if (zswpin < 0) { > + ksft_print_msg("failed to get zswpin\n"); > + goto out; > + } > + > + if (zswpin == 0) { > + ksft_print_msg("zswpin should not be 0\n"); > + goto out; > + } Same here, we can check that zswpin is at least 24M worth of events. Again, not a big deal, but might as well.
