[RFC PATCH v2 4/9] mm/damon: add damos_node_eligible_mem_bp tracepoint
From: Ravi Jonnalagadda <hidden>
Date: 2026-09-10 17:16:39
Also in:
damon, linux-mm, lkml
Subsystem:
damon, memory management, the rest, tracing · Maintainers:
SJ Park, Andrew Morton, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Add a per-tick tracepoint for DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP goal evaluation, exposing the goal target/current values for observability of the node-eligible-memory bandwidth quota loop. Bandwidth-feedback tiering loops read this goal metric to detect convergence. Signed-off-by: Ravi Jonnalagadda <redacted> --- include/trace/events/damon.h | 32 ++++++++++++++++++++++++++++++++ mm/damon/core.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 60 insertions(+)
diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h
index 4dfc9467ea4b5..b2a472eb45d95 100644
--- a/include/trace/events/damon.h
+++ b/include/trace/events/damon.h@@ -74,6 +74,38 @@ TRACE_EVENT(damos_esz, __entry->esz) ); +/* Per-tick DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP goal evaluation. */ +TRACE_EVENT(damos_node_eligible_mem_bp, + + TP_PROTO(unsigned int context_idx, unsigned int scheme_idx, + int nid, + unsigned long target_value, unsigned long current_value), + + TP_ARGS(context_idx, scheme_idx, nid, target_value, current_value), + + TP_STRUCT__entry( + __field(unsigned int, context_idx) + __field(unsigned int, scheme_idx) + __field(int, nid) + __field(unsigned long, target_value) + __field(unsigned long, current_value) + ), + + TP_fast_assign( + __entry->context_idx = context_idx; + __entry->scheme_idx = scheme_idx; + __entry->nid = nid; + __entry->target_value = target_value; + __entry->current_value = current_value; + ), + + TP_printk("ctx_idx=%u scheme_idx=%u nid=%d " + "target_value=%lu current_value=%lu", + __entry->context_idx, __entry->scheme_idx, + __entry->nid, + __entry->target_value, __entry->current_value) +); + TRACE_EVENT_CONDITION(damos_before_apply, TP_PROTO(unsigned int context_idx, unsigned int scheme_idx,
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 991ddb9a09414..6b56a3e961c4e 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c@@ -3461,6 +3461,34 @@ static unsigned long damos_quota_score(struct damon_ctx *c, struct damos *s) highest_score = max(highest_score, mult_frac(goal->current_value, 10000, goal->target_value)); + + /* + * Per-tick visibility of NODE_ELIGIBLE_MEM_BP goal evaluation + * for userspace convergence-detection. + */ + if (goal->metric == DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP && + trace_damos_node_eligible_mem_bp_enabled()) { + /* + * cidx is hardcoded 0 because DAMON sysfs currently + * supports a single context per kdamond. Other DAMOS + * tracepoints (damos_before_apply, damos_esz, + * damos_stat_after_apply_interval) follow the same + * convention; once multi-ctx-per-kdamond lands the + * field becomes meaningful. + */ + unsigned int cidx = 0, sidx = 0; + struct damos *siter; + + damon_for_each_scheme(siter, c) { + if (siter == s) + break; + sidx++; + } + trace_damos_node_eligible_mem_bp(cidx, sidx, + goal->nid, + goal->target_value, + goal->current_value); + } } return highest_score;
--
2.43.0