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b=ox1Of21zf466valLKp99VgE6Npi2m7UHhoXKf5/TUQH6DnfElXxvgH+b8ifIMFE2v xqW2zDm8NqAQ7dUm++XEnYWmeQzWP5RpgtM0B7TOTf24MP7EfMospsQZ7/sgzl/979 vhE16OirDAl6Fiz5ULpEB8KiUY4J+qgVXP2petQuujOnuEA+xirLoGwsa/G5YS10Zq UjMG99NwwvwzJVx71/wKf3oLYTwbzySL4wz7xpZq1DiaCbcS3ysDJqgyOnxn9QO6Ze WiBbCpZXOD3JoefiyU+yrAom6HW/pMrLrpG6QLJ3VFXugz2MLttS/vNNt6GjjTg223 ccDppjdY79y8A== From: SJ Park To: Jinjie Ruan Cc: SJ Park , akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm/damon/reclaim: allow disabling watermarks to force reclaim of cold pages Date: Tue, 27 Oct 2026 06:57:45 -0700 Message-ID: <20261027135746.150166-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <6e381f14-f00b-4c0d-8499-f5a5f37b2572@huawei.com> References: X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CBAE41C0005 X-Spam-Status: No, score=-9.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: 8zmb69m41uz9jwj6qbxszgdwuxidcmwc X-HE-Tag: 1793109474-51476 X-HE-Meta: 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 9rNv9PYs GDSQZVdhQUt9vxln6q48ojiufn+9vbMCLuVRTV1hMzDqtwUp5ZrTsq4jKysBolrhOc3cKLfWXocmpFPQAlVPje1SwKIqemoh3vS9NWP+K39Cia8p8h22hEo3NaD/m7ZhApyH7dGCf4lOteE+Du6NIuWjN369iQMgnzRq+QEByDrUX18tNlso1/uYSokIp/cCFoP2LTTJWknnefuNKdjjWCfNxpV2GyMwC6dr4PBRTZJFh+bP88WtqY9F+qtl4NEip9neW2iOPcGteubg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, 27 Oct 2026 17:46:11 +0800 Jinjie Ruan wrote: > > > 在 2026/10/20 21:58, SJ Park 写道: > > Hello Jinjie, > > > > On Tue, 20 Oct 2026 21:32:33 +0800 Jinjie Ruan wrote: > > > >> DAMON_RECLAIM runs its scheme only while the free memory rate is in > >> [wmarks_low, wmarks_mid]. Reclaiming cold pages raises the rate, so the > >> scheme self-stops as soon as memory looks plentiful again, which is wrong > >> for a VMM parking an idle sandbox that wants cold anonymous pages > >> reclaimed immediately. > >> > >> So add an ignore_wmarks module parameter. When set, the scheme uses > >> DAMOS_WMARK_NONE, so damos_wmark_wait_us() always returns zero and the > >> scheme stays active, bounded only by min_age and the quota. > > > > I agree there could be use cases that doesn't want the watermarks at all. I'd > > like to avoid adding new DAMON_RECLAIM parameters if possible, though. That's > > becasuse DAMON_RECLAIM is introduced to let people use it without complicated > > setups. We will of course add new parameters if really needed, but I want to > > see if there is a good alternative. > > > > Have you considered some other alternatives? For example, could respectively > > setting wmarks_high, wmarks_mid and wmarks_low to 100%, 100% and 0% effectively > > disable watermarks? Have you tried that? If that works, how about updating > > Hi SJ, > > Yes, it does for my use case. Thank you for confirming. > > > document to clearly explain the usage? Also, have you considered using DAMON > > Thank you! I will send a patch to update the doc later. Looking forward to your patch! > > > sysfs interface instead of DAMON_RECLAIM? > > DAMON sysfs can also do this with "none" watermarks. But I want the > simple DAMON_RECLAIM for only proactive reclam. Thank you for clarifying, that makes sense to me. Thanks, SJ [...]