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References: <20231130194023.4102148-1-nphamcs@gmail.com> <20231130194023.4102148-6-nphamcs@gmail.com>
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From:   Chris Li <chrisl@kernel.org>
Date:   Thu, 7 Dec 2023 16:43:18 -0800
Message-ID: <CAF8kJuOdrXHU0RBVZwVXk25nDT__fzWrHiRwW8Jf3seLq882iA@mail.gmail.com>
Subject: Re: [PATCH v8 5/6] selftests: cgroup: update per-memcg zswap
 writeback selftest
To:     Nhat Pham <nphamcs@gmail.com>
Cc:     akpm@linux-foundation.org, hannes@cmpxchg.org,
        cerasuolodomenico@gmail.com, yosryahmed@google.com,
        sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com,
        mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com,
        muchun.song@linux.dev, linux-mm@kvack.org, kernel-team@meta.com,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
        shuah@kernel.org
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Hi Nhat,

Thanks for the self test.

Acked-by: Chris Li <chrisl@kernel.org> (Google)

Chris

On Thu, Nov 30, 2023 at 11:40=E2=80=AFAM Nhat Pham <nphamcs@gmail.com> wrot=
e:
>
> From: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
>
> The memcg-zswap self test is updated to adjust to the behavior change
> implemented by commit 87730b165089 ("zswap: make shrinking memcg-aware"),
> where zswap performs writeback for specific memcg.
>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> Signed-off-by: Nhat Pham <nphamcs@gmail.com>
> ---
>  tools/testing/selftests/cgroup/test_zswap.c | 74 ++++++++++++++-------
>  1 file changed, 50 insertions(+), 24 deletions(-)
>
> diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/=
selftests/cgroup/test_zswap.c
> index c99d2adaca3f..47fdaa146443 100644
> --- a/tools/testing/selftests/cgroup/test_zswap.c
> +++ b/tools/testing/selftests/cgroup/test_zswap.c
> @@ -50,9 +50,9 @@ static int get_zswap_stored_pages(size_t *value)
>         return read_int("/sys/kernel/debug/zswap/stored_pages", value);
>  }
>
> -static int get_zswap_written_back_pages(size_t *value)
> +static int get_cg_wb_count(const char *cg)
>  {
> -       return read_int("/sys/kernel/debug/zswap/written_back_pages", val=
ue);
> +       return cg_read_key_long(cg, "memory.stat", "zswp_wb");
>  }
>
>  static long get_zswpout(const char *cgroup)
> @@ -73,6 +73,24 @@ static int allocate_bytes(const char *cgroup, void *ar=
g)
>         return 0;
>  }
>
> +static char *setup_test_group_1M(const char *root, const char *name)
> +{
> +       char *group_name =3D cg_name(root, name);
> +
> +       if (!group_name)
> +               return NULL;
> +       if (cg_create(group_name))
> +               goto fail;
> +       if (cg_write(group_name, "memory.max", "1M")) {
> +               cg_destroy(group_name);
> +               goto fail;
> +       }
> +       return group_name;
> +fail:
> +       free(group_name);
> +       return NULL;
> +}
> +
>  /*
>   * Sanity test to check that pages are written into zswap.
>   */
> @@ -117,43 +135,51 @@ static int test_zswap_usage(const char *root)
>
>  /*
>   * When trying to store a memcg page in zswap, if the memcg hits its mem=
ory
> - * limit in zswap, writeback should not be triggered.
> - *
> - * This was fixed with commit 0bdf0efa180a("zswap: do not shrink if cgro=
up may
> - * not zswap"). Needs to be revised when a per memcg writeback mechanism=
 is
> - * implemented.
> + * limit in zswap, writeback should affect only the zswapped pages of th=
at
> + * memcg.
>   */
>  static int test_no_invasive_cgroup_shrink(const char *root)
>  {
> -       size_t written_back_before, written_back_after;
>         int ret =3D KSFT_FAIL;
> -       char *test_group;
> +       size_t control_allocation_size =3D MB(10);
> +       char *control_allocation, *wb_group =3D NULL, *control_group =3D =
NULL;
>
>         /* Set up */
> -       test_group =3D cg_name(root, "no_shrink_test");
> -       if (!test_group)
> -               goto out;
> -       if (cg_create(test_group))
> +       wb_group =3D setup_test_group_1M(root, "per_memcg_wb_test1");
> +       if (!wb_group)
> +               return KSFT_FAIL;
> +       if (cg_write(wb_group, "memory.zswap.max", "10K"))
>                 goto out;
> -       if (cg_write(test_group, "memory.max", "1M"))
> +       control_group =3D setup_test_group_1M(root, "per_memcg_wb_test2")=
;
> +       if (!control_group)
>                 goto out;
> -       if (cg_write(test_group, "memory.zswap.max", "10K"))
> +
> +       /* Push some test_group2 memory into zswap */
> +       if (cg_enter_current(control_group))
>                 goto out;
> -       if (get_zswap_written_back_pages(&written_back_before))
> +       control_allocation =3D malloc(control_allocation_size);
> +       for (int i =3D 0; i < control_allocation_size; i +=3D 4095)
> +               control_allocation[i] =3D 'a';
> +       if (cg_read_key_long(control_group, "memory.stat", "zswapped") < =
1)
>                 goto out;
>
> -       /* Allocate 10x memory.max to push memory into zswap */
> -       if (cg_run(test_group, allocate_bytes, (void *)MB(10)))
> +       /* Allocate 10x memory.max to push wb_group memory into zswap and=
 trigger wb */
> +       if (cg_run(wb_group, allocate_bytes, (void *)MB(10)))
>                 goto out;
>
> -       /* Verify that no writeback happened because of the memcg allocat=
ion */
> -       if (get_zswap_written_back_pages(&written_back_after))
> -               goto out;
> -       if (written_back_after =3D=3D written_back_before)
> +       /* Verify that only zswapped memory from gwb_group has been writt=
en back */
> +       if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(control_grou=
p) =3D=3D 0)
>                 ret =3D KSFT_PASS;
>  out:
> -       cg_destroy(test_group);
> -       free(test_group);
> +       cg_enter_current(root);
> +       if (control_group) {
> +               cg_destroy(control_group);
> +               free(control_group);
> +       }
> +       cg_destroy(wb_group);
> +       free(wb_group);
> +       if (control_allocation)
> +               free(control_allocation);
>         return ret;
>  }
>
> --
> 2.34.1
>