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b=SyAFRhvlIwWuXxtyW+DsYxsCGfICLywCNwisc9/R05DvJtWpdXfO+V6YaT9UJRYS5 7yqczLFVhUoBa3jiKUac4MKkaeZf2UzyH8UGuiY6lH4K7GojUiUjy52dxu2T58nvUv F29DoDuvn9S0r+/qz6nm46ufYGH4dVO2Rh1Bgnb/wOCU8US+ZbyyaEYxUl3KSW3UmI pw1ldkWPvsljqcBZZC0J3dnyowVHxs9de1m61hnMxMTbcuV/P8WLw8TjWCl/3c/Nu3 LOJSd/23nPnoB6lKTFsxrkKyWp/djcFqpEZmQ2cg3+4P3FYEd/kGlCqYkP3hnrkX/t lCsfBmpVPRnuw== From: SJ Park To: Lian Wang Cc: SJ Park , damon@lists.linux.dev, linux-mm@kvack.org, daichaobing@sangfor.com.cn, kunwu.chan@gmail.com Subject: Re: [RESEND RFC PATCH v2 4/5] mm/damon: introduce DAMOS_SPLIT action Date: Thu, 2 Jul 2026 13:00:44 -0700 Message-ID: <20260702200045.92126-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260702094633.75658-5-lianux.mm@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspam-User: X-Stat-Signature: u65urn7dc7zoi6u6aqaopzdrji1cszsm X-Rspamd-Queue-Id: E98C080009 X-HE-Tag: 1783022461-198135 X-HE-Meta: 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 zB2S15eA T4Pw0nl4CcAmmmP9d9bPkPAnH9bO0J8V2+F+Z1aSOxxTFamQynH1/AePocSttfN/0L0Kw9Ic+RVVCD7nNIIpwYqDpHF6lcEZOXyYfnaEtlyY6vEnAhgkRwpxIAbnCmLA70gwfHJL3Y2hGvGOqfWNN3RnBNjQo/8Mf69c8fEk9ilbc+w9QnHIsRZH4U0RAH2quz291nQNYBs+FMYM6Vma2beaiot0vW0JvCVi/eO7jMecLb7pg7WiL1E9fijNF9AT9Zvj7Pr6/4a9XHaA20xIqLkrLWsjpbEM2x18ESi3IAE07n4Pw1wLHkToY12vzCwGCCIYSQYxUHrpWDt7pjg/Z0Hd/D5fYnYJx3GFngwX7N93wv6XP1frQiPN2tFu3dfjX5eO3ZcgAST3geL/gWwCe+vHDU4R2nkt9v8HyiT4LS8uEiDxU+YCznBW1qa2NOk3XrRzjRFJ46/dX3og= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 2 Jul 2026 17:46:32 +0800 Lian Wang wrote: > Add DAMOS_SPLIT to the damos_action enum for splitting large folios > into smaller mTHP-order folios. Add a target_order field to struct > damos to specify the desired split order. This commit is not adding but reusing the field. > > Expose the action as "split" through the DAMON sysfs interface with > target_order validation (must be 2..HPAGE_PMD_ORDER-1). > > Signed-off-by: Lian Wang > Signed-off-by: Lian Wang Let's have only one S-o-b: line if there is no reason to have two. > --- > include/linux/damon.h | 9 +++++++-- > mm/damon/sysfs-schemes.c | 16 ++++++++++++++++ > 2 files changed, 23 insertions(+), 2 deletions(-) > > diff --git a/include/linux/damon.h b/include/linux/damon.h > index 5a0587556573..30cf4afb212c 100644 > --- a/include/linux/damon.h > +++ b/include/linux/damon.h > @@ -121,6 +121,7 @@ struct damon_target { > * @DAMOS_HUGEPAGE: Call ``madvise()`` for the region with MADV_HUGEPAGE. > * @DAMOS_NOHUGEPAGE: Call ``madvise()`` for the region with MADV_NOHUGEPAGE. > * @DAMOS_COLLAPSE: Call ``madvise()`` for the region with MADV_COLLAPSE. > + * @DAMOS_SPLIT: Split large folios to the target mTHP order. > * @DAMOS_LRU_PRIO: Prioritize the region on its LRU lists. > * @DAMOS_LRU_DEPRIO: Deprioritize the region on its LRU lists. > * @DAMOS_MIGRATE_HOT: Migrate the regions prioritizing warmer regions. > @@ -141,6 +142,7 @@ enum damos_action { > DAMOS_HUGEPAGE, > DAMOS_NOHUGEPAGE, > DAMOS_COLLAPSE, > + DAMOS_SPLIT, > DAMOS_LRU_PRIO, > DAMOS_LRU_DEPRIO, > DAMOS_MIGRATE_HOT, > @@ -573,8 +575,11 @@ struct damos { > struct damos_access_pattern pattern; > enum damos_action action; > /* > - * @target_order: target order for mTHP actions (DAMOS_COLLAPSE). > - * 0 means system default (PMD order). Valid: 0, 2..HPAGE_PMD_ORDER. > + * @target_order: target mTHP order for DAMOS_COLLAPSE and > + * DAMOS_SPLIT. For COLLAPSE, 0 means PMD order default, > + * valid values: 0, 2..HPAGE_PMD_ORDER. For SPLIT, > + * valid values: 2..HPAGE_PMD_ORDER-1; 0 and HPAGE_PMD_ORDER > + * are rejected at scheme creation time (defaulting to 2). > */ > unsigned int target_order; As I commented to an earlier patch, let's use the union. > unsigned long apply_interval_us; > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c > index 7dcd582ded86..84a4617ca3d3 100644 > --- a/mm/damon/sysfs-schemes.c > +++ b/mm/damon/sysfs-schemes.c > @@ -2293,6 +2293,10 @@ static struct damos_sysfs_action_name damos_sysfs_action_names[] = { > .action = DAMOS_COLLAPSE, > .name = "collapse", > }, > + { > + .action = DAMOS_SPLIT, > + .name = "split", > + }, > { > .action = DAMOS_LRU_PRIO, > .name = "lru_prio", > @@ -3058,11 +3062,23 @@ static struct damos *damon_sysfs_mk_scheme( > HPAGE_PMD_ORDER, HPAGE_PMD_ORDER); > target_order = 0; > } > + if (sysfs_scheme->action == DAMOS_SPLIT && > + (target_order == 0 || > + target_order >= HPAGE_PMD_ORDER)) { > + pr_warn("DAMON split: target_order %u invalid, need 2..%u. Defaulting to 2.\n", > + target_order, > + HPAGE_PMD_ORDER - 1); > + target_order = 2; > + } As I also commented to an earlier patch, this validation will eventually dropped. > #else > if (sysfs_scheme->action == DAMOS_COLLAPSE && target_order != 0) { > pr_warn("DAMON collapse: target_order not supported without THP. Use 0.\n"); > target_order = 0; > } > + if (sysfs_scheme->action == DAMOS_SPLIT) { > + pr_warn("DAMON split: not supported without THP.\n"); > + target_order = 2; Why set target_order here? > + } > #endif > scheme->target_order = target_order; Thanks, SJ