On 2013/8/12 23:26, Karim Yaghmour wrote:
>
> On 13-08-11 11:24 PM, zhangwei(Jovi) wrote:
>> If you want to base on ftrace, below two approach maybe take into use:
>>
>> - register_ftrace_function/unregister_ftrace_function
>>
>> - perf_event_create_kernel_counter (function event id is 1)
>>
>>
On 2013/8/12 23:26, Karim Yaghmour wrote:
On 13-08-11 11:24 PM, zhangwei(Jovi) wrote:
If you want to base on ftrace, below two approach maybe take into use:
- register_ftrace_function/unregister_ftrace_function
- perf_event_create_kernel_counter (function event id is 1)
the first one is
On 13-08-11 11:24 PM, zhangwei(Jovi) wrote:
> If you want to base on ftrace, below two approach maybe take into use:
>
> - register_ftrace_function/unregister_ftrace_function
>
> - perf_event_create_kernel_counter (function event id is 1)
>
> the first one is simplest, IMO.
Thx for the
On 13-08-11 11:24 PM, zhangwei(Jovi) wrote:
If you want to base on ftrace, below two approach maybe take into use:
- register_ftrace_function/unregister_ftrace_function
- perf_event_create_kernel_counter (function event id is 1)
the first one is simplest, IMO.
Thx for the pointers.
On 2013/8/12 8:03, Karim Yaghmour wrote:
>
> Wondering if there's a way for reading perf counters in the kernel. I'd
> like to read/record perf counters on ftrace function tracing
> entries/exits to provide a rundown of the value of various counters on
> function call boundaries.
>
> [ Steven:
On 13-08-11 10:47 PM, Andi Kleen wrote:
> That's what normal sampling already does.
>
> If you're worried about systematic shadow effects just randomize a bit.
That's actually the point. I'd like to be able to study/compare both
approaches. I could be completely off, but I'd like to see if a
> Indeed. It doesn't actually have to be at every single ftrace
> begin/exit. But possibly starting with some kind of every nth and then
> drilling down as the culprit is incrementally singled-out.
That's what normal sampling already does.
If you're worried about systematic shadow effects just
On 13-08-11 10:23 PM, Andi Kleen wrote:
> KVM does it, see arch/x86/kvm/pmu.c. Essentially it would be doing RDPMC.
Thx for the pointer, appreciated.
> But the overhead will be likely very high, some sampling approach
> is likely better.
Indeed. It doesn't actually have to be at every single
Karim Yaghmour writes:
> Wondering if there's a way for reading perf counters in the kernel. I'd
> like to read/record perf counters on ftrace function tracing
> entries/exits to provide a rundown of the value of various counters on
> function call boundaries.
KVM does it, see
Wondering if there's a way for reading perf counters in the kernel. I'd
like to read/record perf counters on ftrace function tracing
entries/exits to provide a rundown of the value of various counters on
function call boundaries.
[ Steven: apologies for sending you a duplicate here of what I
Wondering if there's a way for reading perf counters in the kernel. I'd
like to read/record perf counters on ftrace function tracing
entries/exits to provide a rundown of the value of various counters on
function call boundaries.
[ Steven: apologies for sending you a duplicate here of what I
Karim Yaghmour karim.yaghm...@opersys.com writes:
Wondering if there's a way for reading perf counters in the kernel. I'd
like to read/record perf counters on ftrace function tracing
entries/exits to provide a rundown of the value of various counters on
function call boundaries.
KVM does it,
On 13-08-11 10:23 PM, Andi Kleen wrote:
KVM does it, see arch/x86/kvm/pmu.c. Essentially it would be doing RDPMC.
Thx for the pointer, appreciated.
But the overhead will be likely very high, some sampling approach
is likely better.
Indeed. It doesn't actually have to be at every single
Indeed. It doesn't actually have to be at every single ftrace
begin/exit. But possibly starting with some kind of every nth and then
drilling down as the culprit is incrementally singled-out.
That's what normal sampling already does.
If you're worried about systematic shadow effects just
On 13-08-11 10:47 PM, Andi Kleen wrote:
That's what normal sampling already does.
If you're worried about systematic shadow effects just randomize a bit.
That's actually the point. I'd like to be able to study/compare both
approaches. I could be completely off, but I'd like to see if a
On 2013/8/12 8:03, Karim Yaghmour wrote:
Wondering if there's a way for reading perf counters in the kernel. I'd
like to read/record perf counters on ftrace function tracing
entries/exits to provide a rundown of the value of various counters on
function call boundaries.
[ Steven:
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