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Mon, 05 Feb 2024 15:25:41 -0800 (PST) MIME-Version: 1.0 References: <20240205225608.3083251-1-nphamcs@gmail.com> <20240205225608.3083251-4-nphamcs@gmail.com> In-Reply-To: From: Nhat Pham Date: Mon, 5 Feb 2024 15:25:30 -0800 Message-ID: Subject: Re: [PATCH v3 3/3] selftests: add zswapin and no zswap tests To: Yosry Ahmed Cc: akpm@linux-foundation.org, riel@surriel.com, shuah@kernel.org, hannes@cmpxchg.org, tj@kernel.org, lizefan.x@bytedance.com, roman.gushchin@linux.dev, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C114940002 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: h1a7empmg5qsqbznc3txa8mbf3hnuqs6 X-HE-Tag: 1707175542-955793 X-HE-Meta: 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 RD6PLumF omvtpqsI1hWVKFV6d8nPUaMhHyUbIrZap2T2L4JSbDp4VppLeB63O/Qa1af1VKmxY9WJ1cIiSsfM4pKjFgoxPr0YW9TjFrlzCzgglKSZeMaQxHFWMO3guEyhqKbZSshY9ngsbLYQYFIc4c1ew0Vl9JrXJlVmFjJ7Qimo6iSTBJdqqUGNui+1mARUJzcaKWziXGpX28suhjMQu4vUpEZV3xhewlzZE5Pju/OJWBunw12rSgoFy1RpIg8JmcWwY6fCM4EE0xu+HjQLS57o82GF1UiXipKn6RwPUVZwmG8ryCCx9y+MM65Bpf84Fpy3gGKU3x5L/DwPkcueGqyS3nUCNU7hT0bYCj6IUHcgFIhZBFqxaosQq7EqNkZTWejjp5vocE1NvocV1m/+HlJhs9YaOZxl6gScv7aP2F2PCRVdrgI9/SgGoGq1pKOMISkfEc+zfx4qx86l3Y2o6n+I= X-Bogosity: Ham, tests=bogofilter, spamicity=0.404737, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 5, 2024 at 3:05=E2=80=AFPM Yosry Ahmed = 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 =3D 0, no pages can= go > > to the zswap pool for the cgroup. > > > > Suggested-by: Rik van Riel > > Suggested-by: Yosry Ahmed > > Signed-off-by: Nhat Pham > > LGTM with a few nits below: > Acked-by: Yosry Ahmed > > 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/testin= g/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 =3D (size_t)arg; > > + char *mem =3D (char *)malloc(size); > > + int ret =3D 0; > > + > > + if (!mem) > > + return -1; > > + for (int i =3D 0; i < size; i +=3D 4095) > > + mem[i] =3D 'a'; > > + > > + /* go through the allocated memory to (z)swap in and out pages */ > > nit: s/go/Go > > > + for (int i =3D 0; i < size; i +=3D 4095) { > > + if (mem[i] !=3D 'a') > > + ret =3D -1; > > + } > > + > > + free(mem); > > + return ret; > > +} > > + > > static int allocate_bytes(const char *cgroup, void *arg) > > { > > size_t size =3D (size_t)arg; > > @@ -100,7 +121,6 @@ static int test_zswap_usage(const char *root) > > int ret =3D KSFT_FAIL; > > char *test_group; > > > > - /* Set up */ > > We removed this comment here. > > > test_group =3D 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 =3D 0, no pages can go to the zswa= p pool for > > + * the cgroup. > > + */ > > +static int test_swapin_nozswap(const char *root) > > +{ > > + int ret =3D KSFT_FAIL; > > + char *test_group; > > + long swap_peak, zswpout; > > + > > + test_group =3D 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 =3D 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 =3D=3D 0) { > > + ksft_print_msg("pages should be swapped out\n"); > > + goto out; > > + } > > We can actually check that this number is >=3D 24M instead. Not a big > deal, but might as well. > > > + > > + zswpout =3D 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 =3D 0\= n"); > > + goto out; > > + } > > + > > + ret =3D 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 =3D 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 =3D 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 =3D cg_read_key_long(test_group, "memory.stat", "zswpin ")= ; > > + if (zswpin < 0) { > > + ksft_print_msg("failed to get zswpin\n"); > > + goto out; > > + } > > + > > + if (zswpin =3D=3D 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.