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smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 8304B4041D; Wed, 13 May 2026 18:07:30 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf08.hostedemail.com (Postfix) with ESMTPA id 9F6C220029; Wed, 13 May 2026 18:07:28 +0000 (UTC) Date: Wed, 13 May 2026 14:07:32 -0400 From: Steven Rostedt To: SeongJae Park Cc: Andrew Morton , Masami Hiramatsu , Mathieu Desnoyers , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 18/28] mm/damon: trace probe_hits Message-ID: <20260513140732.2320c563@gandalf.local.home> In-Reply-To: <20260512143645.113201-19-sj@kernel.org> References: <20260512143645.113201-1-sj@kernel.org> <20260512143645.113201-19-sj@kernel.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9F6C220029 X-Stat-Signature: 19k3hjixp4ddabd59xf647tdn9ssb7x4 X-Rspamd-Server: rspamout03 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+XR4QBARvilo/iw685qO7EjLUbgY33/3Y= X-HE-Tag: 1778695648-519701 X-HE-Meta: U2FsdGVkX1+ztHJmbfencz8xskODMPGeCvM+5KKPEYCOFkZBK3DuVA72UQFXfLA2XiaCC1Lrd1TX827gLdPa0yRorEbvVLdnpgaP2F6PcYA57+G4DIsUo7ibScB41ACkwFPSMhmAucYTH00cudknJWH82uLgSDwtPpeXU/Pj4tC+S2F9GUC+0Mv+7Ta3YfAIhlYEMpS0vOK/oevVn/aRifCol3JS+mYZCoMZETyhMcyLWwaV5oT8PfG6LVCWLAHVKsG2gBZvSvI+/RzaE3AkdWg1hUsxpeVQfdTpEWUS0oQwAc84hFbgw8SZW3sCglk3BduJb90ng6hopBuHSDsK1pjZFYjAOl8d On Tue, 12 May 2026 07:36:33 -0700 SeongJae Park wrote: > Introduce a new tracepoint for exposing the per-region per-probe > positive sample count via tracefs. > > Signed-off-by: SeongJae Park > --- > include/trace/events/damon.h | 36 ++++++++++++++++++++++++++++++++++++ > mm/damon/core.c | 7 +++++++ > 2 files changed, 43 insertions(+) > > diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h > index 7e25f4469b81b..d7b94c7640217 100644 > --- a/include/trace/events/damon.h > +++ b/include/trace/events/damon.h > @@ -130,6 +130,42 @@ 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, unsigned int nr_probes), > + > + TP_ARGS(target_id, r, nr_regions, nr_probes), > + > + TP_STRUCT__entry( > + __field(unsigned long, target_id) > + __field(unsigned long, start) > + __field(unsigned long, end) > + __field(unsigned int, nr_regions) > + __field(unsigned int, nr_accesses) > + __field(unsigned int, age) > + __dynamic_array(unsigned char, probe_hits, nr_probes) > + ), > + > + TP_fast_assign( > + __entry->target_id = target_id; > + __entry->start = r->ar.start; > + __entry->end = r->ar.end; > + __entry->nr_regions = nr_regions; > + __entry->nr_accesses = r->nr_accesses; > + __entry->age = r->age; > + memcpy(__get_dynamic_array(probe_hits), r->probe_hits, > + sizeof(*r->probe_hits) * nr_probes); > + ), > + > + TP_printk("target_id=%lu nr_regions=%u %lu-%lu: %u %u probe_hits=%s", > + __entry->target_id, __entry->nr_regions, > + __entry->start, __entry->end, > + __entry->nr_accesses, __entry->age, > + __print_hex(__get_dynamic_array(probe_hits), > + __get_dynamic_array_len(probe_hits))) > +); > + > 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 fe6c789f2cecb..14b15c9876516 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -1905,6 +1905,11 @@ static void kdamond_reset_aggregated(struct damon_ctx *c) > { > struct damon_target *t; > unsigned int ti = 0; /* target's index */ > + unsigned int nr_probes = 0; > + struct damon_probe *probe; > + > + damon_for_each_probe(probe, c) > + nr_probes++; Is the above logic needed when the tracepoint isn't enabled? If not, then you could add: if (trace_damon_aggregated_v2_enabled()) { damon_for_each_probe(probe, c) nr_probes++; } And change the tracepoint to be a conditional tracepoint: TRACE_EVENT_CONDITION(damon_aggregated_v2, TP_PROTO(..), TP_ARGS(..), TP_CONDITION(nr_probes > 0), [..] And then the tracepoint is only triggered if nr_probes is greater than zero (to handle races between the tracepoint being enabled in between the above check and where it triggers). -- Steve > > damon_for_each_target(t, c) { > struct damon_region *r; > @@ -1913,6 +1918,8 @@ 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), > + nr_probes); > damon_warn_fix_nr_accesses_corruption(r); > r->last_nr_accesses = r->nr_accesses; > r->nr_accesses = 0;