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Mon, 13 Apr 2026 01:46:33 -0700 (PDT) X-Received: by 2002:a05:7301:fa0e:b0:2c4:b8d6:45d3 with SMTP id 5a478bee46e88-2d5877991cdmr6669840eec.10.1776069992889; Mon, 13 Apr 2026 01:46:32 -0700 (PDT) MIME-Version: 1.0 References: <20260402063714.55124-1-liwang@redhat.com> <20260402063714.55124-7-liwang@redhat.com> In-Reply-To: From: Li Wang Date: Mon, 13 Apr 2026 16:46:19 +0800 X-Gm-Features: AQROBzATy_Du7HEcqoEpfm3ecefJ913kdNeZVB-cXtC9R6JcAITrAGqsNlgA3uk Message-ID: Subject: Re: [PATCH v6 6/8] selftest/cgroup: fix zswap test_no_invasive_cgroup_shrink on large pagesize system To: Nhat Pham Cc: akpm@linux-foundation.org, rppt@kernel.org, david@kernel.org, hannes@cmpxchg.org, yosry@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, mhocko@suse.com, shuah@kernel.org, chengming.zhou@linux.dev, longman@redhat.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Michal Hocko , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Muchun Song , Tejun Heo , Roman Gushchin , Shakeel Butt , Yosry Ahmed , liwang X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: VmJsSU_VxAAEl3xgRYOsqvL63f_YAeQBxeP70m7tdWk_1776069994 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 9BDD24000A X-Stat-Signature: 5ipa9qxibojcjybssrp3sfp16jdk3rq6 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1776069998-881795 X-HE-Meta: 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 dQr/I/K3 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026 at 8:29=E2=80=AFAM Nhat Pham wrote= : > > On Wed, Apr 1, 2026 at 11:38=E2=80=AFPM Li Wang wrote= : > > > > test_no_invasive_cgroup_shrink sets up two cgroups: wb_group, which is > > expected to trigger zswap writeback, and a control group (renamed to > > zw_group), which should only have pages sitting in zswap without any > > writeback. > > > > There are two problems with the current test: > > > > 1) The data patterns are reversed. wb_group uses allocate_bytes(), whic= h > > writes only a single byte per page =E2=80=94 trivially compressible, > > especially by zstd =E2=80=94 so compressed pages fit within zswap.ma= x and > > writeback is never triggered. Meanwhile, the control group uses > > getrandom() to produce hard-to-compress data, but it is the group > > that does *not* need writeback. > > > > 2) The test uses fixed sizes (10K zswap.max, 10MB allocation) that are > > too small on systems with large PAGE_SIZE (e.g. 64K), failing to > > build enough memory pressure to trigger writeback reliably. > > > > Fix both issues by: > > - Swapping the data patterns: fill wb_group pages with partially > > random data (getrandom for page_size/4 bytes) to resist compression > > and trigger writeback, and fill zw_group pages with simple repeated > > data to stay compressed in zswap. > > - Making all size parameters PAGE_SIZE-aware: set allocation size to > > PAGE_SIZE * 1024, memory.zswap.max to PAGE_SIZE, and memory.max to > > allocation_size / 2 for both cgroups. > > - Allocating memory inline instead of via cg_run() so the pages > > remain resident throughout the test. > > > > =3D=3D=3D Error Log =3D=3D=3D > > # getconf PAGESIZE > > 65536 > > > > # ./test_zswap > > TAP version 13 > > ... > > ok 5 test_zswap_writeback_disabled > > ok 6 # SKIP test_no_kmem_bypass > > not ok 7 test_no_invasive_cgroup_shrink > > I assume the test passed after fix? ;) That's right! This patchset is targeted to thoroughly fix various bugs. I rerun it too many times on various arches. All works well :). > > Signed-off-by: Li Wang > > Cc: Johannes Weiner > > Cc: Michal Hocko > > Cc: Michal Koutn=C3=BD > > Cc: Muchun Song > > Cc: Nhat Pham > > Cc: Tejun Heo > > Cc: Roman Gushchin > > Cc: Shakeel Butt > > Cc: Yosry Ahmed > > --- > > > > Notes: > > v5: > > - Swap data patterns: use getrandom() for wb_group and simple > > memset for zw_group to fix the reversed allocation logic. > > - Rename control_group to zw_group for clarity. > > - Allocate memory inline instead of via cg_run() so pages remai= n > > resident throughout the test. > > > > tools/testing/selftests/cgroup/test_zswap.c | 70 ++++++++++++++------- > > 1 file changed, 49 insertions(+), 21 deletions(-) > > LGTM. Thanks for fixing the tests :) > > Acked-by: Nhat Pham Thanks a lot! --=20 Regards, Li Wang