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
4 4.13 s 2.07 s 1.03 s rwlock:W release_task+0x68
2 2.07 s 2.07 s 1.03 s rwlock:R mm_update_next_owner+0x50
2 2.07 s 2.07 s 1.03 s rwlock:W do_exit+0x338
1 41.56 ms 41.56 ms 41.56 ms mutex cgroup_kn_lock_live+0x58
2 36.12 us 18.83 us 18.06 us rwlock:W do_exit+0x338
changes since v0:
- skip trace_contention functions
- use sym->end instead of __traceiter_contention_end for text_end
Signed-off-by: Anne Macedo <[email protected]>
---
tools/perf/util/machine.c | 17 +++++++++++++++++
tools/perf/util/machine.h | 2 +-
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 527517db3182..db443947ccd1 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -3266,6 +3266,14 @@ 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);
+ machine->traceiter.text_end = map__unmap_ip(kmap, sym->end);
+
+ sym = machine__find_kernel_symbol_by_name(machine, "trace_contention_begin", &kmap);
+ machine->trace.text_start = map__unmap_ip(kmap, sym->start);
+ machine->trace.text_end = map__unmap_ip(kmap, sym->end);
}
/* failed to get kernel symbols */
@@ -3280,5 +3288,14 @@ 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 currently don't have their own section
+ * but we consider them lock functions
+ */
+ if (machine->traceiter.text_start <= addr && addr < machine->traceiter.text_end)
+ return true;
+
+ if (machine->trace.text_start <= addr && addr < machine->trace.text_end)
+ return true;
+
return false;
}
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index e28c787616fe..4312f6db6de0 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, trace;
pid_t *current_tid;
size_t current_tid_sz;
union { /* Tool specific area */
--
2.39.2
Hello Anne,
On Sat, Mar 9, 2024 at 5:27 AM Anne Macedo <[email protected]> wrote:
>
> 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
>
> 4 4.13 s 2.07 s 1.03 s rwlock:W release_task+0x68
> 2 2.07 s 2.07 s 1.03 s rwlock:R mm_update_next_owner+0x50
> 2 2.07 s 2.07 s 1.03 s rwlock:W do_exit+0x338
> 1 41.56 ms 41.56 ms 41.56 ms mutex cgroup_kn_lock_live+0x58
> 2 36.12 us 18.83 us 18.06 us rwlock:W do_exit+0x338
>
> changes since v0:
>
> - skip trace_contention functions
> - use sym->end instead of __traceiter_contention_end for text_end
>
> Signed-off-by: Anne Macedo <[email protected]>
> ---
> tools/perf/util/machine.c | 17 +++++++++++++++++
> tools/perf/util/machine.h | 2 +-
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 527517db3182..db443947ccd1 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -3266,6 +3266,14 @@ 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);
Unlike __sched_text_{start,end} and __lock_text_{start,end} I guess
this traceiter thing is optional so it might not be there. You need to
handle if it's NULL.
I think it depends on the kernel version and configuration. I remember
I saw a different symbol on old kernels. But it'd be hard to handle all
the cases. Let's have a single trace text section in the struct machine
and use __traceiter_contention_begin only. If it's not found you can
fallback to trace_contention_begin.
Thanks,
Namhyung
> + machine->traceiter.text_start = map__unmap_ip(kmap, sym->start);
> + machine->traceiter.text_end = map__unmap_ip(kmap, sym->end);
> +
> + sym = machine__find_kernel_symbol_by_name(machine, "trace_contention_begin", &kmap);
> + machine->trace.text_start = map__unmap_ip(kmap, sym->start);
> + machine->trace.text_end = map__unmap_ip(kmap, sym->end);
> }
>
> /* failed to get kernel symbols */
> @@ -3280,5 +3288,14 @@ 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 currently don't have their own section
> + * but we consider them lock functions
> + */
> + if (machine->traceiter.text_start <= addr && addr < machine->traceiter.text_end)
> + return true;
> +
> + if (machine->trace.text_start <= addr && addr < machine->trace.text_end)
> + return true;
> +
> return false;
> }
> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
> index e28c787616fe..4312f6db6de0 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, trace;
> pid_t *current_tid;
> size_t current_tid_sz;
> union { /* Tool specific area */
> --
> 2.39.2
>
Namhyung Kim <[email protected]> writes:
> Hello Anne,
>
> On Sat, Mar 9, 2024 at 5:27 AM Anne Macedo <[email protected]> wrote:
>>
>> 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
>>
>> 4 4.13 s 2.07 s 1.03 s rwlock:W release_task+0x68
>> 2 2.07 s 2.07 s 1.03 s rwlock:R mm_update_next_owner+0x50
>> 2 2.07 s 2.07 s 1.03 s rwlock:W do_exit+0x338
>> 1 41.56 ms 41.56 ms 41.56 ms mutex cgroup_kn_lock_live+0x58
>> 2 36.12 us 18.83 us 18.06 us rwlock:W do_exit+0x338
>>
>> changes since v0:
>>
>> - skip trace_contention functions
>> - use sym->end instead of __traceiter_contention_end for text_end
>>
>> Signed-off-by: Anne Macedo <[email protected]>
>> ---
>> tools/perf/util/machine.c | 17 +++++++++++++++++
>> tools/perf/util/machine.h | 2 +-
>> 2 files changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>> index 527517db3182..db443947ccd1 100644
>> --- a/tools/perf/util/machine.c
>> +++ b/tools/perf/util/machine.c
>> @@ -3266,6 +3266,14 @@ 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);
>
> Unlike __sched_text_{start,end} and __lock_text_{start,end} I guess
> this traceiter thing is optional so it might not be there. You need to
> handle if it's NULL.
>
Let me test with CONFIG_TRACEPOINTS=n then.
> I think it depends on the kernel version and configuration. I remember
> I saw a different symbol on old kernels. But it'd be hard to handle all
> the cases. Let's have a single trace text section in the struct machine
> and use __traceiter_contention_begin only. If it's not found you can
> fallback to trace_contention_begin.
>
ACK :)
>
> Thanks,
> Namhyung
>
>
>> + machine->traceiter.text_start = map__unmap_ip(kmap, sym->start);
>> + machine->traceiter.text_end = map__unmap_ip(kmap, sym->end);
>> +
>> + sym = machine__find_kernel_symbol_by_name(machine, "trace_contention_begin", &kmap);
>> + machine->trace.text_start = map__unmap_ip(kmap, sym->start);
>> + machine->trace.text_end = map__unmap_ip(kmap, sym->end);
>> }
>>
>> /* failed to get kernel symbols */
>> @@ -3280,5 +3288,14 @@ 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 currently don't have their own section
>> + * but we consider them lock functions
>> + */
>> + if (machine->traceiter.text_start <= addr && addr < machine->traceiter.text_end)
>> + return true;
>> +
>> + if (machine->trace.text_start <= addr && addr < machine->tracetext_end)
>> + return true;
>> +
>> return false;
>> }
>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>> index e28c787616fe..4312f6db6de0 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, trace;
>> pid_t *current_tid;
>> size_t current_tid_sz;
>> union { /* Tool specific area */
>> --
>> 2.39.2
>>
Anne Macedo <[email protected]> writes:
> Namhyung Kim <[email protected]> writes:
>
>> Hello Anne,
>>
>> On Sat, Mar 9, 2024 at 5:27 AM Anne Macedo <[email protected]> wrote:
>>>
>>> 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
>>>
>>> 4 4.13 s 2.07 s 1.03 s rwlock:W release_task+0x68
>>> 2 2.07 s 2.07 s 1.03 s rwlock:R mm_update_next_owner+0x50
>>> 2 2.07 s 2.07 s 1.03 s rwlock:W do_exit+0x338
>>> 1 41.56 ms 41.56 ms 41.56 ms mutex cgroup_kn_lock_live+0x58
>>> 2 36.12 us 18.83 us 18.06 us rwlock:W do_exit+0x338
>>>
>>> changes since v0:
>>>
>>> - skip trace_contention functions
>>> - use sym->end instead of __traceiter_contention_end for text_end
>>>
>>> Signed-off-by: Anne Macedo <[email protected]>
>>> ---
>>> tools/perf/util/machine.c | 17 +++++++++++++++++
>>> tools/perf/util/machine.h | 2 +-
>>> 2 files changed, 18 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>> index 527517db3182..db443947ccd1 100644
>>> --- a/tools/perf/util/machine.c
>>> +++ b/tools/perf/util/machine.c
>>> @@ -3266,6 +3266,14 @@ 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);
>>
>> Unlike __sched_text_{start,end} and __lock_text_{start,end} I guess
>> this traceiter thing is optional so it might not be there. You need to
>> handle if it's NULL.
>>
>
> Let me test with CONFIG_TRACEPOINTS=n then.
>
Thanks for pointing out, with CONFIG_TRACEPOINTS=n perf lock contention
won't work, but I tried with a faux symbol and got a segfault. v2 will
handle that.
>
>> I think it depends on the kernel version and configuration. I remember
>> I saw a different symbol on old kernels. But it'd be hard to handle all
>> the cases. Let's have a single trace text section in the struct machine
>> and use __traceiter_contention_begin only. If it's not found you can
>> fallback to trace_contention_begin.
However, if we fallback to trace_contention_begin, we won't be able to
filter out both __traceiter_contention_begin and trace_contention_begin
at the same time.
>>
> ACK :)
>>
>> Thanks,
>> Namhyung
>>
>>
>>> + machine->traceiter.text_start = map__unmap_ip(kmap, sym->start);
>>> + machine->traceiter.text_end = map__unmap_ip(kmap, sym->end);
>>> +
>>> + sym = machine__find_kernel_symbol_by_name(machine, "trace_contention_begin", &kmap);
>>> + machine->trace.text_start = map__unmap_ip(kmap, sym->start);
>>> + machine->trace.text_end = map__unmap_ip(kmap, sym->end);
>>> }
>>>
>>> /* failed to get kernel symbols */
>>> @@ -3280,5 +3288,14 @@ 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 currently don't have their own section
>>> + * but we consider them lock functions
>>> + */
>>> + if (machine->traceiter.text_start <= addr && addr < machine->traceiter.text_end)
>>> + return true;
>>> +
>>> + if (machine->trace.text_start <= addr && addr < machine->trace.text_end)
>>> + return true;
>>> +
>>> return false;
>>> }
>>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>>> index e28c787616fe..4312f6db6de0 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, trace;
>>> pid_t *current_tid;
>>> size_t current_tid_sz;
>>> union { /* Tool specific area */
>>> --
>>> 2.39.2
>>>
Thanks, Anne
On Mon, Mar 11, 2024 at 07:25:16PM +0000, Anne Macedo wrote:
> Anne Macedo <[email protected]> writes:
> > Namhyung Kim <[email protected]> writes:
> >> I think it depends on the kernel version and configuration. I remember
> >> I saw a different symbol on old kernels. But it'd be hard to handle all
> >> the cases. Let's have a single trace text section in the struct machine
> >> and use __traceiter_contention_begin only. If it's not found you can
> >> fallback to trace_contention_begin.
> However, if we fallback to trace_contention_begin, we won't be able to
> filter out both __traceiter_contention_begin and trace_contention_begin
> at the same time.
I think for ARM we need to skip both, no? I.e. I agree with Anne.
- Arnaldo
On Mon, Mar 11, 2024 at 12:53 PM Arnaldo Carvalho de Melo
<[email protected]> wrote:
>
> On Mon, Mar 11, 2024 at 07:25:16PM +0000, Anne Macedo wrote:
> > Anne Macedo <[email protected]> writes:
> > > Namhyung Kim <[email protected]> writes:
> > >> I think it depends on the kernel version and configuration. I remember
> > >> I saw a different symbol on old kernels. But it'd be hard to handle all
> > >> the cases. Let's have a single trace text section in the struct machine
> > >> and use __traceiter_contention_begin only. If it's not found you can
> > >> fallback to trace_contention_begin.
>
> > However, if we fallback to trace_contention_begin, we won't be able to
> > filter out both __traceiter_contention_begin and trace_contention_begin
> > at the same time.
>
> I think for ARM we need to skip both, no? I.e. I agree with Anne.
I haven't tested it on ARM, please go ahead if it is needed.
Thanks,
Namhyung