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AJvYcCWgnD9MjcTcHo6trtSNHsUA1Ppk8o/iGbvxtDIpQJVr5hFVFk/bW6/iQwKIVLsRa7BKNCFFG8vXjw==@kvack.org X-Gm-Message-State: AOJu0YyznWrS1Z5SMTTvb+A74PtRzTS8ej/0tHg/XAxsPQx54KzPpkLg nlKfGEjSdgEBXdf6SMy5R2m0vtn+cRdx1ZoBSIImo3BSawfjpXBfn9C266DdNUf+ADbPFKvYHfn Vog9rl3EGbDrOXxayIWRl6bkXIzZj6RI= X-Gm-Gg: AY/fxX4OUvoW6LlWgpulIoFRlaxd8Nu5Io7pkfdgMxWG066IPWhGYrOGbrlDOK3U63L Hrxjcm5c+KGJi29mGhVokDFy0yIxf4P4WOyKzatWoOesxZa+bxVLy0E3LdDr6Ujm+yEEmH5NAGK opQZn71V/LNlAl/w+yB236y8vh25F8ezTBtJ0i4EFdAaPdl3hx9eymkOOyQIML7aVIKVKrzCsHu 8jiH1SxHBeTVdZGYfEXVIiCGdEvbcEuCtML1EgVyJpEs6SixBrLgvP/Y+y2Y19TTE+/z+ucnefT P/PKdxFQmFc7GZfcN41wtk9yyxjzxYC8OA== X-Google-Smtp-Source: AGHT+IEDYC3cY6soBRLQg0jrKD+eKmTD2ovAt2yrZmq93YN5K8GrT0NaJGJRys7cFEZm4N+ttZhDuYFIVnybaRJXjUM= X-Received: by 2002:a05:6214:27c2:b0:87c:1d24:7b7f with SMTP id 6a1803df08f44-890841aa05fmr191022996d6.23.1768053313735; Sat, 10 Jan 2026 05:55:13 -0800 (PST) MIME-Version: 1.0 References: <20260108101535.50696-1-akinobu.mita@gmail.com> <20260108101535.50696-4-akinobu.mita@gmail.com> In-Reply-To: From: Akinobu Mita Date: Sat, 10 Jan 2026 22:55:02 +0900 X-Gm-Features: AZwV_QiB1arM2112x9CFryUSneEVqs_KakkkX2Yd9ULOgdOZCKyZki0KapMs8FI Message-ID: Subject: Re: [PATCH v3 3/3] mm/vmscan: don't demote if there is not enough free memory in the lower memory tier To: gourry@gourry.net Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, bingjiao@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B658440009 X-Rspamd-Server: rspam06 X-Stat-Signature: xir8oq5fitmeg7qcrkggagp9r8ig91aj X-Rspam-User: X-HE-Tag: 1768053314-404436 X-HE-Meta: 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 8EzYQSTJ Tpt1FXtFX5lridnHYmjrgpuSIQbnY1BtMgb1FyH9w4z48A3S6fJ6p7wEj48FLE7RQMw1I3EhZeZ0TN01sRaP9iO41FA7aKJ0whZNRhoqqmcwv5hOxU1vpgUmeIbBRRTYdIVsZgn+WOrQYrczYjjZU5WJRTTErLvUNR6P2nWWRQyKfuhljSlbj+Ye4PCdutJy4CDlURxF8q91waVocl110dFgOIfe4TEo+afYTnH4BetuOiD5pPSbeRutGJrGdc7TzzeWthfUNU+wNVjqG8TdBfJLJkDFfKzYRUsrFlH9dIMMDt9v5b2iIS9niSNv7pLZtFqb2b39PhIb61+qC9zK1AkAghQ5tg7kkj/9/+ew1PXHJRP6QaT+BGjfn4YxLxKgBhq+VETEtb2oslBRyQuwbavgM9y8XveyLUiO472JAbYd/pBMGb67Yr127IEeNzS898f5GqU8HKX5H90FWMKYxbarygwj19uiOYbuG X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 2026=E5=B9=B41=E6=9C=8810=E6=97=A5(=E5=9C=9F) 1:08 Gregory Price : > > > + for_each_node_mask(nid, allowed_mask) { > > + int z; > > + struct zone *zone; > > + struct pglist_data *pgdat =3D NODE_DATA(nid); > > + > > + for_each_managed_zone_pgdat(zone, pgdat, z, MAX_NR_ZONES = - 1) { > > + if (zone_watermark_ok(zone, 0, min_wmark_pages(zo= ne), > > + ZONE_MOVABLE, 0)) > > Why does this only check zone movable? Here, zone_watermark_ok() checks the free memory for all zones from 0 to MAX_NR_ZONES - 1. There is no strong reason to pass ZONE_MOVABLE as the highest_zoneidx argument every time zone_watermark_ok() is called; I can change it if an appropriate value is found. In v1, highest_zoneidx was "sc ? sc->reclaim_idx : MAX_NR_ZONES - 1" > Also, would this also limit pressure-signal to invoke reclaim when > there is still swap space available? Should demotion not be a pressure > source for triggering harder reclaim? Since can_reclaim_anon_pages() checks whether there is free space on the sw= ap device before checking with can_demote(), I think the negative impact of th= is change will be small. However, since I have not been able to confirm the behavior when a swap device is available, I would like to correctly underst= and the impact.