Re: [PATCH V2 4/4] sh: Use the perf-events backend for oprofile

Robert Richter
2010-08-27T15:01:26Z

On 26.08.10 15:09:19, Matt Fleming wrote:
> Use the perf-events based wrapper for oprofile available in
> drivers/oprofile. This allows us to centralise the code to control
> performance counters.
>
> Signed-off-by: Matt Fleming <matt@console-pimps.org>
> ---
>
> Paul,
>
> I dropped the CONFIG_PERF_EVENTS dependency from the Makefile in this
> version because to do anything useful we need perf events anyway.

Initialization should simply fail with a printk message for this case,
implement function stubs for the !CONFIG_PERF_EVENTS case instead in
the oprofile.h header file.

>
> arch/sh/oprofile/Makefile | 2 +-
> arch/sh/oprofile/common.c | 96 ++++++++-----------------------------------
> arch/sh/oprofile/op_impl.h | 33 ---------------
> 3 files changed, 19 insertions(+), 112 deletions(-)
> delete mode 100644 arch/sh/oprofile/op_impl.h
>
> diff --git a/arch/sh/oprofile/Makefile b/arch/sh/oprofile/Makefile
> index 4886c5c..e1015ae 100644
> --- a/arch/sh/oprofile/Makefile
> +++ b/arch/sh/oprofile/Makefile
> @@ -4,6 +4,6 @@ DRIVER_OBJS = $(addprefix ../../../drivers/oprofile/, \
> oprof.o cpu_buffer.o buffer_sync.o \
> event_buffer.o oprofile_files.o \
> oprofilefs.o oprofile_stats.o \
> - timer_int.o )
> + timer_int.o oprofile_perf.o )
>
> oprofile-y := $(DRIVER_OBJS) common.o backtrace.o
> diff --git a/arch/sh/oprofile/common.c b/arch/sh/oprofile/common.c
> index ac60493..f8d4a84 100644
> --- a/arch/sh/oprofile/common.c
> +++ b/arch/sh/oprofile/common.c
> @@ -17,71 +17,23 @@
> #include <linux/init.h>
> #include <linux/errno.h>
> #include <linux/smp.h>
> +#include <linux/perf_event.h>

I don't see a reason why this must be included here.

It's only for sh_pmu_name() and sh_pmu_num_events(), so the interface
looks wrong here. It should be in oprofile_perf.c. The functions
should be generic non-arch perf code. See below.

> #include <asm/processor.h>
> -#include "op_impl.h"
> -
> -static struct op_sh_model *model;
> -
> -static struct op_counter_config ctr[20];
>
> extern void sh_backtrace(struct pt_regs * const regs, unsigned int depth);
>
> -static int op_sh_setup(void)
> -{
> - /* Pre-compute the values to stuff in the hardware registers. */
> - model->reg_setup(ctr);
> -
> - /* Configure the registers on all cpus. */
> - on_each_cpu(model->cpu_setup, NULL, 1);
> -
> - return 0;
> -}
> -
> -static int op_sh_create_files(struct super_block *sb, struct dentry *root)
> -{
> - int i, ret = 0;
> -
> - for (i = 0; i < model->num_counters; i++) {
> - struct dentry *dir;
> - char buf[4];
> -
> - snprintf(buf, sizeof(buf), "%d", i);
> - dir = oprofilefs_mkdir(sb, root, buf);
> -
> - ret |= oprofilefs_create_ulong(sb, dir, "enabled", &ctr[i].enabled);
> - ret |= oprofilefs_create_ulong(sb, dir, "event", &ctr[i].event);
> - ret |= oprofilefs_create_ulong(sb, dir, "kernel", &ctr[i].kernel);
> - ret |= oprofilefs_create_ulong(sb, dir, "user", &ctr[i].user);
> -
> - if (model->create_files)
> - ret |= model->create_files(sb, dir);
> - else
> - ret |= oprofilefs_create_ulong(sb, dir, "count", &ctr[i].count);
> -
> - /* Dummy entries */
> - ret |= oprofilefs_create_ulong(sb, dir, "unit_mask", &ctr[i].unit_mask);
> - }
> -
> - return ret;
> -}
> -
> -static int op_sh_start(void)
> +static char *op_name_from_perf_name(const char *name)
> {
> - /* Enable performance monitoring for all counters. */
> - on_each_cpu(model->cpu_start, NULL, 1);
> + if (!strcmp(name, "SH-4A"))
> + return "sh/sh4a";
> + if (!strcmp(name, "SH7750"))
> + return "sh/sh7750";

With that implementation we always have to touch the code for new
cpus. Maybe we derive it from the perf name, e.g. making all lowercase
and removing dashes?

>
> - return 0;
> -}
> -
> -static void op_sh_stop(void)
> -{
> - /* Disable performance monitoring for all counters. */
> - on_each_cpu(model->cpu_stop, NULL, 1);
> + return NULL;
> }
>
> int __init oprofile_arch_init(struct oprofile_operations *ops)
> {
> - struct op_sh_model *lmodel = NULL;
> int ret;
>
> /*
> @@ -91,40 +43,28 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
> */
> ops->backtrace = sh_backtrace;
>
> - /*
> - * XXX
> - *
> - * All of the SH7750/SH-4A counters have been converted to perf,
> - * this infrastructure hook is left for other users until they've
> - * had a chance to convert over, at which point all of this
> - * will be deleted.
> - */
> -
> - if (!lmodel)
> - return -ENODEV;
> if (!(current_cpu_data.flags & CPU_HAS_PERF_COUNTER))
> return -ENODEV;
>
> - ret = lmodel->init();
> - if (unlikely(ret != 0))
> - return ret;
> + ops->setup = oprofile_perf_setup;
> + ops->create_files = oprofile_perf_create_files;
> + ops->start = oprofile_perf_start;
> + ops->stop = oprofile_perf_stop;
> + ops->cpu_type = op_name_from_perf_name(sh_pmu_name());
>
> - model = lmodel;
> + oprofile_perf_set_num_counters(sh_pmu_num_events());
>
> - ops->setup = op_sh_setup;
> - ops->create_files = op_sh_create_files;
> - ops->start = op_sh_start;
> - ops->stop = op_sh_stop;
> - ops->cpu_type = lmodel->cpu_type;
> + ret = oprofile_perf_init();

Instead of exporting all the functions above implement something like:

name = op_name_from_perf_name(sh_pmu_name());
num_events = sh_pmu_num_events();
ret = oprofile_perf_init(ops, name, num_events);

We will then have only oprofile_perf_init() and oprofile_perf_exit()
as interface which is much cleaner.

-Robert

> + if (ret != 0)
> + return ret;
>
> printk(KERN_INFO "oprofile: using %s performance monitoring.\n",
> - lmodel->cpu_type);
> + ops->cpu_type);
>
> return 0;
> }
>
> void oprofile_arch_exit(void)
> {
> - if (model && model->exit)
> - model->exit();
> + oprofile_perf_exit();
> }

--
Advanced Micro Devices, Inc.
Operating System Research Center