On Sat, 3 Oct 2026 13:27:27 -0700 Ravi Jonnalagadda <[email protected]> wrote:
> Add a tracepoint for DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP quota goal > evaluation. The tracepoint fires once per quota-score computation when > the goal metric is DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP, exposing > context_idx, scheme_idx, nid, target_value, and current_value. > current_value is reported as the quota tuning sees it, after the goal's > complement setting is applied. > > The DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP metric expresses node memory > occupancy as basis points of eligible bytes. This information is not > exposed through any existing external interface (perf stat, /proc, or > sysfs), so the tracepoint is the only way for userspace to observe the > target and current eligible-memory basis point values at quota-scoring > time. > > Link: > https://lore.kernel.org/linux-mm/[email protected]/ > Signed-off-by: Ravi Jonnalagadda <[email protected]> > --- > include/trace/events/damon.h | 31 +++++++++++++++++++++++++++++++ > mm/damon/core.c | 16 ++++++++++++++++ > 2 files changed, 47 insertions(+) > > diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h > index 8851727ae162..2c7249cc7c88 100644 > --- a/include/trace/events/damon.h > +++ b/include/trace/events/damon.h > @@ -74,6 +74,37 @@ 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) Can you move the nid after the two unsigned long values below. This creates a structure, and on 64bit machines, this adds a 4 byte padding in the middle of the ring buffer. > + __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 b63e60ef8990..6ddd15dc4f55 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -3294,6 +3294,22 @@ 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)); > + > + if (goal->metric == DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP && > + trace_damos_node_eligible_mem_bp_enabled()) { If you move the trace_damos_node_eligible_mem_bp_enabled() before the goal->metric check, you will save yourself a branch when tracing is off. As the trace_*_enabled() is a static branch (nop or jmp) it has no cmp branch, but the above will keep the goal->metric still exposed. By swapping the two compares, the goal->metric check will be hidder behind the 'nop' when tracing is disabled. -- Steve > + 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; > > base-commit: 763ad0211c7b587344f03bc4d1299810aeb736f4
