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From: Anne Macedo <retpolanne@posteo.net>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>
Cc: Anne Macedo <retpolanne@posteo.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Ian Rogers <irogers@google.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-perf-users@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v0] perf lock contention: skip traceiter functions
Date: Fri,  8 Mar 2024 12:03:31 +0000
Message-Id: <20240308120332.372810-1-retpolanne@posteo.net>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

The perf lock contention program currently shows the caller of the locks
as __traceiter_contention_begin+0x??. This caller can be ignored, as it is
from the traceiter itself. Instead, it should show the real callers for
the locks.

When fiddling with the --stack-skip parameter, the actual callers for
the locks start to show up. However, just ignore the
__traceiter_contention_begin and the __traceiter_contention_end symbols
so the actual callers will show up.

Before this patch is applied:

sudo perf lock con -a -b -- sleep 3
 contended   total wait     max wait     avg wait         type   caller

         8      2.33 s       2.28 s     291.18 ms     rwlock:W   __traceiter_contention_begin+0x44
         4      2.33 s       2.28 s     582.35 ms     rwlock:W   __traceiter_contention_begin+0x44
         7    140.30 ms     46.77 ms     20.04 ms     rwlock:W   __traceiter_contention_begin+0x44
         2     63.35 ms     33.76 ms     31.68 ms        mutex   trace_contention_begin+0x84
         2     46.74 ms     46.73 ms     23.37 ms     rwlock:W   __traceiter_contention_begin+0x44
         1     13.54 us     13.54 us     13.54 us        mutex   trace_contention_begin+0x84
         1      3.67 us      3.67 us      3.67 us      rwsem:R   __traceiter_contention_begin+0x44

Before this patch is applied - using --stack-skip 5

sudo perf lock con --stack-skip 5 -a -b -- sleep 3
 contended   total wait     max wait     avg wait         type   caller

         2      2.24 s       2.24 s       1.12 s      rwlock:W   do_epoll_wait+0x5a0
         4      1.65 s     824.21 ms    412.08 ms     rwlock:W   do_exit+0x338
         2    824.35 ms    824.29 ms    412.17 ms     spinlock   get_signal+0x108
         2    824.14 ms    824.14 ms    412.07 ms     rwlock:W   release_task+0x68
         1     25.22 ms     25.22 ms     25.22 ms        mutex   cgroup_kn_lock_live+0x58
         1     24.71 us     24.71 us     24.71 us     spinlock   do_exit+0x44
         1     22.04 us     22.04 us     22.04 us      rwsem:R   lock_mm_and_find_vma+0xb0

After this patch is applied:

sudo ./perf lock con -a -b -- sleep 3
 contended   total wait     max wait     avg wait         type   caller

         6      5.27 s       1.76 s     878.55 ms     rwlock:W   release_task+0x68
         2      2.99 s       2.99 s       1.50 s      spinlock   do_send_sig_info+0x3c
         2      1.77 s       1.77 s     884.39 ms     spinlock   sigprocmask+0x98
         2      1.76 s       1.76 s     878.56 ms     rwlock:W   do_exit+0x338
         2      1.76 s       1.76 s     878.55 ms     rwlock:W   release_task+0x68
         5      1.76 s       1.76 s     351.41 ms     rwlock:W   do_exit+0x338
         1     48.10 ms     48.10 ms     48.10 ms        mutex   trace_contention_begin+0x84
         4    257.80 us    119.34 us     64.45 us     spinlock   get_signal+0x108
         1      9.33 us      9.33 us      9.33 us     rwlock:W   do_exit+0x338

Signed-off-by: Anne Macedo <retpolanne@posteo.net>
---
 tools/perf/util/machine.c | 10 ++++++++++
 tools/perf/util/machine.h |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 527517db3182..8e729167c1aa 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -3266,6 +3266,12 @@ bool machine__is_lock_function(struct machine *machine, u64 addr)
 
 		sym = machine__find_kernel_symbol_by_name(machine, "__lock_text_end", &kmap);
 		machine->lock.text_end = map__unmap_ip(kmap, sym->start);
+
+		sym = machine__find_kernel_symbol_by_name(machine, "__traceiter_contention_begin", &kmap);
+		machine->traceiter.text_start = map__unmap_ip(kmap, sym->start);
+
+		sym = machine__find_kernel_symbol_by_name(machine, "__traceiter_contention_end", &kmap);
+		machine->traceiter.text_end = map__unmap_ip(kmap, sym->start);
 	}
 
 	/* failed to get kernel symbols */
@@ -3280,5 +3286,9 @@ bool machine__is_lock_function(struct machine *machine, u64 addr)
 	if (machine->lock.text_start <= addr && addr < machine->lock.text_end)
 		return true;
 
+	/* traceiter functions are in traceiter text section  */
+	if (machine->traceiter.text_start <= addr && addr < machine->traceiter.text_end)
+		return true;
+
 	return false;
 }
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index e28c787616fe..ec51e9b080b9 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -49,7 +49,7 @@ struct machine {
 	struct {
 		u64	  text_start;
 		u64	  text_end;
-	} sched, lock;
+	} sched, lock, traceiter;
 	pid_t		  *current_tid;
 	size_t		  current_tid_sz;
 	union { /* Tool specific area */
-- 
2.39.2