Re: [RFC PATCH 16/19] mm/damon: trace probe_hits

Steven Rostedt
2026-04-28T18:17:40Z

On Sun, 26 Apr 2026 13:52:17 -0700
SeongJae Park <sj@kernel.org> wrote:

> Introduce a new tracepoint for exposing the per-region per-probe
> positive sample count via tracefs.
>
> Signed-off-by: SeongJae Park <sj@kernel.org>
> ---
> include/trace/events/damon.h | 41 ++++++++++++++++++++++++++++++++++++
> mm/damon/core.c | 1 +
> 2 files changed, 42 insertions(+)
>
> diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h
> index 7e25f4469b81b..121d7bc3a2c27 100644
> --- a/include/trace/events/damon.h
> +++ b/include/trace/events/damon.h
> @@ -130,6 +130,47 @@ TRACE_EVENT(damon_monitor_intervals_tune,
> TP_printk("sample_us=%lu", __entry->sample_us)
> );
>
> +TRACE_EVENT(damon_aggregated_v2,
> +
> + TP_PROTO(unsigned int target_id, struct damon_region *r,
> + unsigned int nr_regions),
> +
> + TP_ARGS(target_id, r, nr_regions),
> +
> + TP_STRUCT__entry(
> + __field(unsigned long, target_id)
> + __field(unsigned int, nr_regions)

Move the nr_regions to after "end" as on 64 bit machines, this creates a 4
byte hole.

-- Steve

> + __field(unsigned long, start)
> + __field(unsigned long, end)
> + __field(unsigned int, nr_accesses)
> + __field(unsigned int, age)
> + __field(unsigned char, probe_hit0)
> + __field(unsigned char, probe_hit1)
> + __field(unsigned char, probe_hit2)
> + __field(unsigned char, probe_hit3)
> + ),
> +
> + TP_fast_assign(
> + __entry->target_id = target_id;
> + __entry->nr_regions = nr_regions;
> + __entry->start = r->ar.start;
> + __entry->end = r->ar.end;
> + __entry->nr_accesses = r->nr_accesses;
> + __entry->age = r->age;
> + __entry->probe_hit0 = r->probe_hits[0];
> + __entry->probe_hit1 = r->probe_hits[1];
> + __entry->probe_hit2 = r->probe_hits[2];
> + __entry->probe_hit3 = r->probe_hits[3];
> + ),
> +
> + TP_printk("target_id=%lu nr_regions=%u %lu-%lu: %u %u %hhu %hhu %hhu %hhu",
> + __entry->target_id, __entry->nr_regions,
> + __entry->start, __entry->end,
> + __entry->nr_accesses, __entry->age,
> + __entry->probe_hit0, __entry->probe_hit1,
> + __entry->probe_hit2, __entry->probe_hit3)
> +);
> +
> TRACE_EVENT(damon_aggregated,
>
> TP_PROTO(unsigned int target_id, struct damon_region *r,
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index fe14971d72747..54834b74efef4 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1924,6 +1924,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
> int i;
>
> trace_damon_aggregated(ti, r, damon_nr_regions(t));
> + trace_damon_aggregated_v2(ti, r, damon_nr_regions(t));
> damon_warn_fix_nr_accesses_corruption(r);
> r->last_nr_accesses = r->nr_accesses;
> r->nr_accesses = 0;