| Message ID | 20240205225608.3083251-4-nphamcs@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fix and extend zswap kselftests | expand |
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 <riel@surriel.com> > Suggested-by: Yosry Ahmed <yosryahmed@google.com> > Signed-off-by: Nhat Pham <nphamcs@gmail.com> LGTM with a few nits below: Acked-by: Yosry Ahmed <yosryahmed@google.com> 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.
On Mon, Feb 5, 2024 at 3:05 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > 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 <riel@surriel.com> > > Suggested-by: Yosry Ahmed <yosryahmed@google.com> > > Signed-off-by: Nhat Pham <nphamcs@gmail.com> > > LGTM with a few nits below: > Acked-by: Yosry Ahmed <yosryahmed@google.com> > > 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 :) Urgh I am stupid :) I meant to remove this, but accidentally removed it from the old test instead :) > > > + 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.
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 */ + 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 */ 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; + } + + 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 */ + 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; + } + + ret = KSFT_PASS; + +out: + cg_destroy(test_group); + free(test_group); + return ret; +} + /* * When trying to store a memcg page in zswap, if the memcg hits its memory * limit in zswap, writeback should affect only the zswapped pages of that @@ -309,6 +425,8 @@ struct zswap_test { const char *name; } tests[] = { T(test_zswap_usage), + T(test_swapin_nozswap), + T(test_zswapin), T(test_no_kmem_bypass), T(test_no_invasive_cgroup_shrink), };
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 <riel@surriel.com> Suggested-by: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Nhat Pham <nphamcs@gmail.com> --- tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++- 1 file changed, 119 insertions(+), 1 deletion(-)