From de6632aa7851b987d8f54129e43d75bc681f72b9 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Tue, 29 Sep 2026 01:01:04 -0700 Subject: [PATCH] mm/damon/core: introduce damos_quota_goal->complement Patch series "mm/damon: introduce damos quota goal target metric complement flag". Aim-oriented DAMOS quota auto-tuning assumes the aggressiveness of the scheme (quota) and the quota goal metric are directly proportional. Depending on the scheme setup and usage, keeping the relationship can be challenging. For example, let's suppose a memory tiering approach for higher upper tier utilization. One common idea for that (TPP) is utilizing two schemes, one for promotion and the other one for demotion. The promotion scheme migrates hot pages from lower tier to upper tier, aiming for high utilization of the upper tier. The demotion scheme migrates cold pages from upper tier to lower tier, aiming for head room free memory of the upper tier. Both schemes and their goals are in direct proportion. However, for this kind of use case, we need to implement two different goal metrics (per-node memory utilization and free memory ratio) while essentially the free memory ratio is just a complemented value of the utilization. To avoid adding too many new metrics, we are adding metrics that turn out to be really needed for each found use case. For example, some_mem_psi_us, node_eligible_mem_bp and hugepage_mem_bp don't have their complemented value version. But it is not really difficult to expect use cases that their complemented version can be useful. For example, hugepage_mem_bp use case may need a way to reduce the hugepage ratio. That would require a complemented version of hugepage_mem_bp. Adding a new metric for each of such use cases could make the number of metrics unnecessarily high, and discourage flexible usages of DAMOS. Add a new flag, quota goal complement, to allow flexible tuning goal setup without unnecessarily increasing the number of metrics. The flag specifies whether to use the complemented value of the given goal metric for the tuning. For example, if the complement flag is set, the upper tier memory utilization ratio metric works the same as the free memory ratio metric for the tier. This patch (of 8): Introduce damos_quota_goal->complement for specifying whether to use a complemented value of the given goal target metric. Add the field to the data structure and implement essential core support. Handle the flag in the quota goal commit and current quota goal metric value retrieval. [akpm@linux-foundation.org: fix comment tpyo, per Gutierrez] Link: https://lore.kernel.org/20260929080113.41708-1-sj@kernel.org Link: https://lore.kernel.org/20260929080113.41708-2-sj@kernel.org Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: Gutierrez Asier --- include/linux/damon.h | 2 ++ mm/damon/core.c | 26 +++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/include/linux/damon.h b/include/linux/damon.h index 6a29dc2ac8db..42234839ce29 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -169,6 +169,7 @@ enum damos_quota_goal_metric { /** * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal. * @metric: Metric to be used for representing the goal. + * @complement: Use the complement of the metric. * @target_value: Target value of @metric to achieve with the tuning. * @current_value: Current value of @metric. * @nid: Node id. @@ -191,6 +192,7 @@ enum damos_quota_goal_metric { */ struct damos_quota_goal { enum damos_quota_goal_metric metric; + bool complement; unsigned long target_value; unsigned long current_value; /* metric-dependent fields */ diff --git a/mm/damon/core.c b/mm/damon/core.c index 5ecbea5d71e1..0d27f08b350e 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1224,6 +1224,7 @@ static int damos_commit_quota_goal( if (!src->target_value) return -EINVAL; dst->metric = src->metric; + dst->complement = src->complement; dst->target_value = src->target_value; if (dst->metric == DAMOS_QUOTA_USER_INPUT) dst->current_value = src->current_value; @@ -2960,10 +2961,18 @@ static void damos_set_psi_current_val(u64 now_psi_total, struct damos_quota_goal *goal, struct damos *s) { u64 last_psi_total = goal->last_psi_total; + unsigned long val; goal->last_psi_total = now_psi_total; if (last_psi_total != U64_MAX) { - goal->current_value = now_psi_total - last_psi_total; + val = now_psi_total - last_psi_total; + if (goal->complement) { + if (val < s->quota.reset_interval * 1000) + val = s->quota.reset_interval * 1000 - val; + else + val = 0; + } + goal->current_value = val; return; } /* uninitialized last_psi_total; make no effect this round */ @@ -3255,6 +3264,21 @@ static void damos_set_quota_goal_current_value(struct damon_ctx *c, default: break; } + if (!goal->complement) + return; + + /* update current_value to complemented value */ + + /* for user_input, users set complemented value on their own */ + if (goal->metric == DAMOS_QUOTA_USER_INPUT) + return; + /* damos_set_psi_current_val() handles complement flag itself */ + if (goal->metric == DAMOS_QUOTA_SOME_MEM_PSI_US) + return; + if (goal->current_value < 10000) + goal->current_value = 10000 - goal->current_value; + else + goal->current_value = 0; } /* Return the highest score since it makes schemes least aggressive */