[PATCH] powerpc/perf: Fix task context setting for trace imc

[PATCH] powerpc/perf: Fix task context setting for trace imc

[Athira Rajeev]

Trace IMC (In-Memory collection counters) in powerpc is
useful for application level profiling. For trace_imc,
presently task context (task_ctx_nr) is set to
perf_hw_context. But perf_hw_context is to be used for
cpu PMU. So for trace_imc, even though it is per thread
PMU, it is preferred to use sw_context inorder to be able
to do application level monitoring. Hence change the
task_ctx_nr to use perf_sw_context.

Fixes: 012ae244845f ("powerpc/perf: Trace imc PMU functions")
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
---
 arch/powerpc/perf/imc-pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index e106909ff9c3..f3b3262bdf02 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -1457,7 +1457,7 @@ static int trace_imc_event_init(struct perf_event *event)
 
 	event->hw.idx = -1;
 
-	event->pmu->task_ctx_nr = perf_hw_context;
+	event->pmu->task_ctx_nr = perf_sw_context;
 	event->destroy = reset_global_refc;
 	return 0;
 }
-- 
2.33.0

Re: [PATCH] powerpc/perf: Fix task context setting for trace imc

[Michael Ellerman]

Athira Rajeev <atrajeev@linux.vnet.ibm.com> writes:
> Trace IMC (In-Memory collection counters) in powerpc is
> useful for application level profiling. For trace_imc,
> presently task context (task_ctx_nr) is set to
> perf_hw_context. But perf_hw_context is to be used for
> cpu PMU. So for trace_imc, even though it is per thread
> PMU, it is preferred to use sw_context inorder to be able
> to do application level monitoring. Hence change the
> task_ctx_nr to use perf_sw_context.

It's not a software event though, so this is not obviously correct.

Can you explain more why this is OK, I guess perf_sw_context is misnamed
these days? And can you add a comment in the code explaining why this
hardware PMU is using perf_sw_context.

cheers

> Fixes: 012ae244845f ("powerpc/perf: Trace imc PMU functions")
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
> ---
>  arch/powerpc/perf/imc-pmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
> index e106909ff9c3..f3b3262bdf02 100644
> --- a/arch/powerpc/perf/imc-pmu.c
> +++ b/arch/powerpc/perf/imc-pmu.c
> @@ -1457,7 +1457,7 @@ static int trace_imc_event_init(struct perf_event *event)
>  
>  	event->hw.idx = -1;
>  
> -	event->pmu->task_ctx_nr = perf_hw_context;
> +	event->pmu->task_ctx_nr = perf_sw_context;
>  	event->destroy = reset_global_refc;
>  	return 0;
>  }
> -- 
> 2.33.0