Re: [PATCH v5 09/22] cpufreq: amd: add trace for amd-pstate module

[Huang Rui]

On Fri, Dec 17, 2021 at 02:12:41AM +0800, Rafael J. Wysocki wrote:
> On Tue, Nov 30, 2021 at 1:38 PM Huang Rui <ray.huang@xxxxxxx> wrote:
> >
> > Add trace event to monitor the performance value changes which is
> > controlled by cpu governors.
> 
> This would need an ACK from Steve.
> 
> >
> > Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> > ---
> >  drivers/cpufreq/Makefile           |  6 ++-
> >  drivers/cpufreq/amd-pstate-trace.c |  2 +
> >  drivers/cpufreq/amd-pstate-trace.h | 77 ++++++++++++++++++++++++++++++
> 
> Why are these two extra files necessary?

Please see below answer.

> 
> >  drivers/cpufreq/amd-pstate.c       |  4 ++
> >  4 files changed, 88 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/cpufreq/amd-pstate-trace.c
> >  create mode 100644 drivers/cpufreq/amd-pstate-trace.h
> >
> > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> > index c8d307010922..285de70af877 100644
> > --- a/drivers/cpufreq/Makefile
> > +++ b/drivers/cpufreq/Makefile
> > @@ -17,6 +17,10 @@ obj-$(CONFIG_CPU_FREQ_GOV_ATTR_SET)  += cpufreq_governor_attr_set.o
> >  obj-$(CONFIG_CPUFREQ_DT)               += cpufreq-dt.o
> >  obj-$(CONFIG_CPUFREQ_DT_PLATDEV)       += cpufreq-dt-platdev.o
> >
> > +# Traces
> > +CFLAGS_amd-pstate-trace.o               := -I$(src)
> > +amd_pstate-y                           := amd-pstate.o amd-pstate-trace.o
> > +
> >  ##################################################################################
> >  # x86 drivers.
> >  # Link order matters. K8 is preferred to ACPI because of firmware bugs in early
> > @@ -25,7 +29,7 @@ obj-$(CONFIG_CPUFREQ_DT_PLATDEV)      += cpufreq-dt-platdev.o
> >  # speedstep-* is preferred over p4-clockmod.
> >
> >  obj-$(CONFIG_X86_ACPI_CPUFREQ)         += acpi-cpufreq.o
> > -obj-$(CONFIG_X86_AMD_PSTATE)           += amd-pstate.o
> > +obj-$(CONFIG_X86_AMD_PSTATE)           += amd_pstate.o
> >  obj-$(CONFIG_X86_POWERNOW_K8)          += powernow-k8.o
> >  obj-$(CONFIG_X86_PCC_CPUFREQ)          += pcc-cpufreq.o
> >  obj-$(CONFIG_X86_POWERNOW_K6)          += powernow-k6.o
> > diff --git a/drivers/cpufreq/amd-pstate-trace.c b/drivers/cpufreq/amd-pstate-trace.c
> > new file mode 100644
> > index 000000000000..891b696dcd69
> > --- /dev/null
> > +++ b/drivers/cpufreq/amd-pstate-trace.c
> > @@ -0,0 +1,2 @@
> > +#define CREATE_TRACE_POINTS
> > +#include "amd-pstate-trace.h"
> > diff --git a/drivers/cpufreq/amd-pstate-trace.h b/drivers/cpufreq/amd-pstate-trace.h
> > new file mode 100644
> > index 000000000000..647505957d4f
> > --- /dev/null
> > +++ b/drivers/cpufreq/amd-pstate-trace.h
> > @@ -0,0 +1,77 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * amd-pstate-trace.h - AMD Processor P-state Frequency Driver Tracer
> > + *
> > + * Copyright (C) 2021 Advanced Micro Devices, Inc. All Rights Reserved.
> > + *
> > + * Author: Huang Rui <ray.huang@xxxxxxx>
> > + */
> > +
> > +#if !defined(_AMD_PSTATE_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
> > +#define _AMD_PSTATE_TRACE_H
> > +
> > +#include <linux/cpufreq.h>
> > +#include <linux/tracepoint.h>
> > +#include <linux/trace_events.h>
> > +
> > +#undef TRACE_SYSTEM
> > +#define TRACE_SYSTEM amd_cpu
> > +
> > +#undef TRACE_INCLUDE_FILE
> > +#define TRACE_INCLUDE_FILE amd-pstate-trace
> > +
> > +#define TPS(x)  tracepoint_string(x)
> > +
> > +TRACE_EVENT(amd_pstate_perf,
> 
> Could this be added to include/trace/events/power.h ?
> 

Actually, that is my original idea, but once I move the trace into
include/trace/events/power.h, the amd-pstate driver cannot build as "ko"
anymore. This is the early stage, "ko" is friendly and flexible for us to
switch and compare between amd-pstate and acpi-cpufreq. I can move it into
"power" trace events once we address the performance issue on shared memory
solution.

Thanks,
Ray