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Mon, 20 Jul 2026 03:02:43 -0700 (PDT) From: Lian Wang To: Gutierrez Asier Cc: Lian Wang , damon@lists.linux.dev, linux-mm@kvack.org, sj@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, npache@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, daichaobing@sangfor.com.cn, wangkefeng.wang@huawei.com, zengheng4@huawei.com, kasong@tencent.com, corbet@lwn.net, skhan@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, lianux.wang@processmission.com, kunwu.chan@linux.dev Subject: Re: [RFC PATCH v3 1/3] mm/damon: introduce DAMOS_SPLIT action Date: Mon, 20 Jul 2026 18:02:32 +0800 Message-ID: <20260720100232.32500-1-lianux.mm@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 20 Jul 2026 12:47:23 +0300 Gutierrez Asier wrote: > > > On 7/20/2026 6:03 AM, Lian Wang wrote: > > Add a new DAMOS action, DAMOS_SPLIT, that splits large folios in the > > target region down to a smaller order. A new per-scheme field and sysfs > > file, target_order, selects the split target: 0 for order-0 base pages, > > or 2..HPAGE_PMD_ORDER-1 for a smaller mTHP order (order-1 is rejected at > > store time since anonymous THPs cannot be split to order-1). > > > > Unlike DAMOS_COLLAPSE which builds large folios, splitting only dismantles > > them; it allocates nothing, copies nothing, and no THP admission policy > > applies. khugepaged deliberately refuses to collapse a folio to a > > smaller order, leaving the shrink direction to callers like this one. > > > > This patch adds the DAMOS_SPLIT action, the ``order`` field (placed in > > the existing union alongside target_nid and migrate_dests), its sysfs > > interface, and documentation. The vaddr operations set handler is added > > in the next patch. > > > > Link: https://lore.kernel.org/20260605161422.213817-9-npache@redhat.com/ > > ("mm/khugepaged: skip collapsing mTHP to smaller orders") Hi Asier, Thanks for the review. All three points noted -- will address them in the next revision along with feedback from David and others. Thanks, Lian Wang