From 4835e2871321fd9cf5bc9702dded323e3e3fbc1a Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Tue, 13 Jan 2026 07:27:06 -0800 Subject: [PATCH] mm/damon/core: introduce [in]active memory ratio damos quota goal metric Patch series "mm/damon: advance DAMOS-based LRU sorting". DAMOS_LRU_[DE]PRIO actions were added to DAMOS for more access-aware LRU lists sorting. For simple usage, a specialized kernel module, namely DAMON_LRU_SORT, has also been introduced. After the introduction of the module, DAMON got a few important new features, including the aim-based quota auto-tuning, age tracking, young page filter, and monitoring intervals auto-tuning. Meanwhile, DAMOS-based LRU sorting had no direct updates. Now we show some rooms to advance for DAMOS-based LRU sorting. Firstly, the aim-oriented quota auto-tuning can simplify the LRU sorting parameters tuning. But there is no good auto-tuning target metric for LRU sorting use case. Secondly, the behavior of DAMOS_LRU_[DE]PRIO are not very symmetric. DAMOS_LRU_DEPRIO directly moves the pages to inactive LRU list, while DAMOS_LRU_PRIO only marks the page as accessed, so that the page can not directly but only eventually moved to the active LRU list. Finally, DAMON_LRU_SORT users cannot utilize the modern features that can be useful for them, too. Improve the situation with the following changes. First, introduce a new DAMOS quota auto-tuning target metric for active:inactive memory size ratio. Since LRU sorting is a kind of balancing of active and inactive pages, the active:inactive memory size ratio can be intuitively set. Second, update DAMOS_LRU_[DE]PRIO behaviors to be more intuitive and symmetric, by letting them directly move the pages to [in]active LRU list. Third, update the DAMON_LRU_SORT module user interface to be able to fully utilize the modern features including the [in]active memory size ratio-based quota auto-tuning, young page filter, and monitoring intervals auto-tuning. With these changes, for example, users can now ask DAMON to "find hot/cold memory regions with auto-tuned monitoring intervals, do one more page level access check for found hot/cold memory, and move pages of those to active or inactive LRU lists accordingly, aiming X:Y active to inactive memory ratio." For example, if they know 30% of the memory is better to be protected from reclamation, 30:70 can be set as the target ratio. Test Results ------------ I ran DAMON_LRU_SORT with the features introduced by this series, on a real world server workload. For the active:inactive ratio goal, I set 50:50. I confirmed it achieves the target active:inactive ratio, without manual tuning of the monitoring intervals and the hot/coldness thresholds. The baseline system that was not running the DAMON_LRU_SORT was keeping active:inactive ratio of about 1:10. Note that the test didn't show a clear performance difference, though. I believe that was mainly because the workload was not very memory intensive. Also, whether the 50:50 target ratio was optimum is unclear. Nonetheless, the positive performance impact of the basic LRU sorting idea is already confirmed with the initial DAMON_LRU_SORT introduction patch series. The goal of this patch series is simplifying the parameters tuning of DAMOS-based LRU sorting, and the test confirmed the aimed goals are achieved. Patches Sequence ---------------- First three patches extend DAMOS quota auto-tuning to support [in]active memory ratio target metric type. Those (patches 1-3) introduce new metrics, implement DAMON sysfs support, and update the documentation, respectively. Following patch (patch 4) makes DAMOS_LRU_PRIO action to directly move target pages to active LRU list, instead of only marking them accessed. Following seven patches (patches 5-11) updates DAMON_LRU_SORT to support modern DAMON features. Patch 5 makes it uses not only access frequency but also age at under-quota regions prioritization. Patches 6-11 add the support for young page filtering, active:inactive memory ratio based quota auto-tuning, and monitoring intervals auto-tuning, with appropriate document updates. This patch (of 11): DAMOS_LRU_[DE]PRIO are DAMOS actions for making balance of active and inactive memory size. There is no appropriate DAMOS quota auto-tuning target metric for the use case. Add two new DAMOS quota goal metrics for the purpose, namely DAMOS_QUOTA_[IN]ACTIVE_MEM_BP. Those will represent the ratio of [in]active memory to total (inactive + active) memory. Hence, users will be able to ask DAMON to, for example, "find hot and cold memory, and move pages of those to active and inactive LRU lists, adjusting the hot/cold thresholds aiming 50:50 active:inactive memory ratio." Link: https://lkml.kernel.org/r/20260113152717.70459-1-sj@kernel.org Link: https://lkml.kernel.org/r/20260113152717.70459-2-sj@kernel.org Signed-off-by: SeongJae Park Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/damon.h | 4 ++++ mm/damon/core.c | 22 ++++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/linux/damon.h b/include/linux/damon.h index 650e7ecfa32b8..26fb8e90dff68 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -155,6 +155,8 @@ enum damos_action { * @DAMOS_QUOTA_NODE_MEM_FREE_BP: MemFree ratio of a node. * @DAMOS_QUOTA_NODE_MEMCG_USED_BP: MemUsed ratio of a node for a cgroup. * @DAMOS_QUOTA_NODE_MEMCG_FREE_BP: MemFree ratio of a node for a cgroup. + * @DAMOS_QUOTA_ACTIVE_MEM_BP: Active to total LRU memory ratio. + * @DAMOS_QUOTA_INACTIVE_MEM_BP: Inactive to total LRU memory ratio. * @NR_DAMOS_QUOTA_GOAL_METRICS: Number of DAMOS quota goal metrics. * * Metrics equal to larger than @NR_DAMOS_QUOTA_GOAL_METRICS are unsupported. @@ -166,6 +168,8 @@ enum damos_quota_goal_metric { DAMOS_QUOTA_NODE_MEM_FREE_BP, DAMOS_QUOTA_NODE_MEMCG_USED_BP, DAMOS_QUOTA_NODE_MEMCG_FREE_BP, + DAMOS_QUOTA_ACTIVE_MEM_BP, + DAMOS_QUOTA_INACTIVE_MEM_BP, NR_DAMOS_QUOTA_GOAL_METRICS, }; diff --git a/mm/damon/core.c b/mm/damon/core.c index 6888917c1a00f..729a5f7fac94e 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2132,6 +2132,23 @@ static unsigned long damos_get_node_memcg_used_bp( } #endif +/* + * Returns LRU-active or inactive memory to total LRU memory size ratio. + */ +static unsigned int damos_get_in_active_mem_bp(bool active_ratio) +{ + unsigned long active, inactive, total; + + /* This should align with /proc/meminfo output */ + active = global_node_page_state(NR_LRU_BASE + LRU_ACTIVE_ANON) + + global_node_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE); + inactive = global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_ANON) + + global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE); + total = active + inactive; + if (active_ratio) + return active * 10000 / total; + return inactive * 10000 / total; +} static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal) { @@ -2154,6 +2171,11 @@ static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal) case DAMOS_QUOTA_NODE_MEMCG_FREE_BP: goal->current_value = damos_get_node_memcg_used_bp(goal); break; + case DAMOS_QUOTA_ACTIVE_MEM_BP: + case DAMOS_QUOTA_INACTIVE_MEM_BP: + goal->current_value = damos_get_in_active_mem_bp( + goal->metric == DAMOS_QUOTA_ACTIVE_MEM_BP); + break; default: break; } -- 2.47.3