[PATCH v0] perf lock contention: skip traceiter functions
From: Anne Macedo
Date: Fri Mar 08 2024 - 07:13:43 EST
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@xxxxxxxxxx>
---
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