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Fri, 25 Jul 2025 10:35:46 -0700 (PDT) Received: from localhost ([2a03:2880:25ff:42::]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e8df871bab0sm138800276.45.2025.07.25.10.35.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jul 2025 10:35:46 -0700 (PDT) From: Joshua Hahn To: Andrew Morton , David Hildenbrand , Johannes Weiner Cc: Zi Yan , Matthew Brost , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: [PATCH] mempolicy: Clarify what RECLAIM_ZONE means Date: Fri, 25 Jul 2025 10:35:45 -0700 Message-ID: <20250725173546.2295177-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The zone_reclaim_mode API controls reclaim behavior when a node runs out of memory. Contrary to its user-facing name, it is internally referred to as "node_reclaim_mode". This is slightly confusing but there is not much we can do given that it has already been exposed to userspace (since at least 2.6). However, what we can do is to make sure the internal description of what the bits inside zone_reclaim_mode aligns with what it does in practice. Setting RECLAIM_ZONE does indeed run shrink_inactive_list, but a more holis= tic description would be to explain that zone reclaim modulates whether page allocation (and khugepaged collapsing) prefers reclaiming & attempting to allocate locally or should fall back to the next node in the zonelist. Change the description to clarify what zone reclaim entails. Signed-off-by: Joshua Hahn --- include/uapi/linux/mempolicy.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h index 1f9bb10d1a47..24083809d920 100644 --- a/include/uapi/linux/mempolicy.h +++ b/include/uapi/linux/mempolicy.h @@ -69,7 +69,7 @@ enum { * These bit locations are exposed in the vm.zone_reclaim_mode sysctl * ABI. New bits are OK, but existing bits can never change. */ -#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ +#define RECLAIM_ZONE (1<<0) /* Prefer reclaiming & allocating locally */ #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */ =20 base-commit: 25fae0b93d1d7ddb25958bcb90c3c0e5e0e202bd --=20 2.47.3