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h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=rA8piUuDVFXKQYUsfrjwk6SaEVW+aIAdCTLFC3sNlVOzwGiPKiQZU1ZBSikNbvUWt 4Acz8vgJGkGrocuoJVXBHZGhdvb3j3Fz7smyS2aHMocoCPqtL1Fa0EaYhflf5oJxx2 D+jLJGWHgUYTnQ5t11eseHtl1+dSi1QIDLVShM20IJMYOyUr1MZYC2qSDGDpKWv9Vh VIMkPvixw1SBlKil0/ZRRTICkLZvbgqo4Pb++7CnAv4ffb546afArIAiPKQFKwjwnz FtQEqjUjtkLlfXC43LtftVvAJ4uqgBMXXhC6G5u/BTcjRCPEA+jL1w3W/14We73tQ0 tCv4hxESzn3ew== Received: by mail-ej1-f53.google.com with SMTP id a640c23a62f3a-b96d784828bso232305966b.3 for ; Thu, 12 Mar 2026 15:44:47 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCUD9mrXmGM6R18R9ovY6nAzWspH7QMWSoOaHFJFV/1QjjmQ9kqg2x0LJ4/X0K3Y1w1E6vZgY6Qkhg==@kvack.org X-Gm-Message-State: AOJu0YzrQ/vPNuyBTquG8hviERQ8/wQ9VM9vjdcSg0R2zTAkrfSQag9F EtD80cLJ6zgUgK5HK/lPLZ27j/2u7IluvzUIpfQLN1hRXH5uCMHkdPD7Y33JXtohb81aTtM1zwb to6lOrkjwwrnIR3pLVKlaELVInYxv030= X-Received: by 2002:a17:906:3184:b0:b88:7431:3942 with SMTP id a640c23a62f3a-b97651d185emr51530266b.33.1773355486758; Thu, 12 Mar 2026 15:44:46 -0700 (PDT) MIME-Version: 1.0 References: <20260312040627.55257-1-liwang@redhat.com> <20260312040627.55257-7-liwang@redhat.com> In-Reply-To: <20260312040627.55257-7-liwang@redhat.com> From: Yosry Ahmed Date: Thu, 12 Mar 2026 15:44:35 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AaiRm524PNfkYxfVrpc2St54DerNH44DRfyB07Ocb7QbsQotuUYK5q2n16rFokU Message-ID: Subject: Re: [PATCH v2 7/7] selftest/cgroup: fix zswap attempt_writeback() on 64K pagesize system To: Li Wang Cc: mkoutny@suse.com, yosryahmed@google.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Michal Hocko , Muchun Song , Nhat Pham , Tejun Heo , Roman Gushchin , Shakeel Butt Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: uhd9uajf1f9w3mpzj5c4w1en8ze7d4am X-Rspam-User: X-Rspamd-Queue-Id: C81AC1C0005 X-Rspamd-Server: rspam12 X-HE-Tag: 1773355488-437147 X-HE-Meta: U2FsdGVkX18z5ZFhWSd09PLQY+jAFDiaMCiFWetpGOScntG5fOf3cjsjtMXnRjyx/nCWTZEyjcyV9XXOpq/PvRU3h/GHqLfZL1/KWxN/YU4IrG/PBKFNTmZqPSYTS7lCOuS5EBTFtmHsCDrZmZniIyfO1W/sokNu3DAEbPZPTB42KC7sqKtgxoF0Ncx0apG4SMTKYn9yebV8KEiBYP5bIWHjQtVpoGAAMrs9a7ns4NGmgr9UzlE62P10jvelXhCR5NcRdLKuciPHEZxOYnxm848a99Ts/nXRTL/ihJ81p3omflpBuHVoN1p947DEAPn8Q7ovm6+so8VdjEgfm3KtwGPxOT9IHSEYzjYm29OGwOpSwzJgNZkqZAt/WPpEZjNJ7OArn9oSr0S5Ia3Vi++9qi++0kXxmtChu21JswMT18UOBmloQsaEAZcyF90tCrQocx1ZrNxGtjvl41MnW/ddsl4ypjefWLqqW+8VCQy5GzM6NHujWbNxIOb3iqFN9YSnMFvmYVX+dsfmbymNdLNWdPSjES9h07ZMJ8RtCSAv2+Bi8LDAsZ/waVt3JOTCfRXX3ohko6LrchuG807gcS/2oTuHFifpWA49SB4nfZL1MgpkBbkI0877K6RrrUdXWX3L5dR9ju2WcIEAVXqY11wkL8eyWgmOB6JvyHJlx4vu4ZKsDVEyvuH/mVs6lH2o753kZSTB24MqOoBPu/54z/oz7mIzrR+V7nE1IpoaSelSvReAN1wn5Ooxloc6fVSRX1RoyyTzQJT8Cy6TXkQKYfvmQoWhlZVPhtOPPth85ALDymkOtVGcO9h+KqQ2p57EJzu8sIG/ewRjMfFeafUr9inlhTYTeBMUnKixp7d1AZ8NnEZZ4uwVNG6gqK/EUgsL9xbpXVcerW6skEPdmlEqYv7hSkcdIB0B8mDBJorSjKvYTQUE2nDK0Miixzs4K/kzRlmK8sVF7/bmbN5443kyR8G iUb36Rwn C3TpIrVSaqynbOB1PYDnPSNmtj3yZ+5sjEEfp Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 11, 2026 at 9:07=E2=80=AFPM Li Wang wrote: > > In attempt_writeback(), a memsize of 4M only covers 64 pages on 64K > page size systems. When memory.reclaim is called, the kernel prefers > reclaiming clean file pages (binary, libc, linker, etc.) over swapping > anonymous pages. With only 64 pages of anonymous memory, the reclaim > target can be largely or entirely satisfied by dropping file pages, > resulting in very few or zero anonymous pages being pushed into zswap. > > This causes zswap_usage to be extremely small or zero, making > zswap_usage/2 insufficient to create meaningful writeback pressure. > The test then fails because no writeback is triggered. > > On 4K page size systems this is not an issue because 4M covers 1024 > pages, and file pages are a small fraction of the reclaim target. > > Fix this by always allocating 1024 pages regardless of page size. > This ensures enough anonymous pages to reliably populate zswap and > trigger writeback, while keeping the original 4M allocation on 4K > page size systems. > > =3D=3D=3D Error Log =3D=3D=3D > # uname -rm > 6.12.0-211.el10.ppc64le ppc64le > > # getconf PAGESIZE > 65536 > > # ./test_zswap > TAP version 13 > 1..7 > ok 1 test_zswap_usage > ok 2 test_swapin_nozswap > ok 3 test_zswapin > not ok 4 test_zswap_writeback_enabled > ... > > 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 Acked-by: Yosry Ahmed