selftests: Add test of PMU instruction counting on powerpc

This commit adds a test of instruction counting using the PMU on powerpc.

Although the bulk of the code is architecture agnostic, the code needs to
run a precisely sized loop which is implemented in assembler.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Ellerman 2013-08-06 17:42:37 +10:00 committed by Benjamin Herrenschmidt
parent 2fae0d7ced
commit cb96143def
6 changed files with 349 additions and 1 deletions

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@ -13,7 +13,7 @@ CFLAGS := -Wall -O2 -flto -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(CUR
export CC CFLAGS
TARGETS =
TARGETS = pmu
endif

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@ -0,0 +1,23 @@
noarg:
$(MAKE) -C ../
PROGS := count_instructions
EXTRA_SOURCES := ../harness.c event.c
all: $(PROGS)
$(PROGS): $(EXTRA_SOURCES)
# loop.S can only be built 64-bit
count_instructions: loop.S count_instructions.c $(EXTRA_SOURCES)
$(CC) $(CFLAGS) -m64 -o $@ $^
run_tests: all
@-for PROG in $(PROGS); do \
./$$PROG; \
done;
clean:
rm -f $(PROGS) loop.o
.PHONY: all run_tests clean

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@ -0,0 +1,135 @@
/*
* Copyright 2013, Michael Ellerman, IBM Corp.
* Licensed under GPLv2.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <sys/prctl.h>
#include "event.h"
#include "utils.h"
extern void thirty_two_instruction_loop(u64 loops);
static void setup_event(struct event *e, u64 config, char *name)
{
event_init_opts(e, config, PERF_TYPE_HARDWARE, name);
e->attr.disabled = 1;
e->attr.exclude_kernel = 1;
e->attr.exclude_hv = 1;
e->attr.exclude_idle = 1;
}
static int do_count_loop(struct event *events, u64 instructions,
u64 overhead, bool report)
{
s64 difference, expected;
double percentage;
prctl(PR_TASK_PERF_EVENTS_ENABLE);
/* Run for 1M instructions */
thirty_two_instruction_loop(instructions >> 5);
prctl(PR_TASK_PERF_EVENTS_DISABLE);
event_read(&events[0]);
event_read(&events[1]);
expected = instructions + overhead;
difference = events[0].result.value - expected;
percentage = (double)difference / events[0].result.value * 100;
if (report) {
event_report(&events[0]);
event_report(&events[1]);
printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);
printf("Expected %llu\n", expected);
printf("Actual %llu\n", events[0].result.value);
printf("Delta %lld, %f%%\n", difference, percentage);
}
event_reset(&events[0]);
event_reset(&events[1]);
if (difference < 0)
difference = -difference;
/* Tolerate a difference below 0.0001 % */
difference *= 10000 * 100;
if (difference / events[0].result.value)
return -1;
return 0;
}
/* Count how many instructions it takes to do a null loop */
static u64 determine_overhead(struct event *events)
{
u64 current, overhead;
int i;
do_count_loop(events, 0, 0, false);
overhead = events[0].result.value;
for (i = 0; i < 100; i++) {
do_count_loop(events, 0, 0, false);
current = events[0].result.value;
if (current < overhead) {
printf("Replacing overhead %llu with %llu\n", overhead, current);
overhead = current;
}
}
return overhead;
}
static int count_instructions(void)
{
struct event events[2];
u64 overhead;
setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, "instructions");
setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, "cycles");
if (event_open(&events[0])) {
perror("perf_event_open");
return -1;
}
if (event_open_with_group(&events[1], events[0].fd)) {
perror("perf_event_open");
return -1;
}
overhead = determine_overhead(events);
printf("Overhead of null loop: %llu instructions\n", overhead);
/* Run for 1M instructions */
FAIL_IF(do_count_loop(events, 0x100000, overhead, true));
/* Run for 10M instructions */
FAIL_IF(do_count_loop(events, 0xa00000, overhead, true));
/* Run for 100M instructions */
FAIL_IF(do_count_loop(events, 0x6400000, overhead, true));
/* Run for 1G instructions */
FAIL_IF(do_count_loop(events, 0x40000000, overhead, true));
event_close(&events[0]);
event_close(&events[1]);
return 0;
}
int main(void)
{
return test_harness(count_instructions, "count_instructions");
}

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@ -0,0 +1,105 @@
/*
* Copyright 2013, Michael Ellerman, IBM Corp.
* Licensed under GPLv2.
*/
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include "event.h"
int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu,
int group_fd, unsigned long flags)
{
return syscall(__NR_perf_event_open, attr, pid, cpu,
group_fd, flags);
}
void event_init_opts(struct event *e, u64 config, int type, char *name)
{
memset(e, 0, sizeof(*e));
e->name = name;
e->attr.type = type;
e->attr.config = config;
e->attr.size = sizeof(e->attr);
/* This has to match the structure layout in the header */
e->attr.read_format = PERF_FORMAT_TOTAL_TIME_ENABLED | \
PERF_FORMAT_TOTAL_TIME_RUNNING;
}
void event_init_named(struct event *e, u64 config, char *name)
{
event_init_opts(e, config, PERF_TYPE_RAW, name);
}
#define PERF_CURRENT_PID 0
#define PERF_NO_CPU -1
#define PERF_NO_GROUP -1
int event_open_with_options(struct event *e, pid_t pid, int cpu, int group_fd)
{
e->fd = perf_event_open(&e->attr, pid, cpu, group_fd, 0);
if (e->fd == -1) {
perror("perf_event_open");
return -1;
}
return 0;
}
int event_open_with_group(struct event *e, int group_fd)
{
return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, group_fd);
}
int event_open(struct event *e)
{
return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, PERF_NO_GROUP);
}
void event_close(struct event *e)
{
close(e->fd);
}
int event_reset(struct event *e)
{
return ioctl(e->fd, PERF_EVENT_IOC_RESET);
}
int event_read(struct event *e)
{
int rc;
rc = read(e->fd, &e->result, sizeof(e->result));
if (rc != sizeof(e->result)) {
fprintf(stderr, "read error on event %p!\n", e);
return -1;
}
return 0;
}
void event_report_justified(struct event *e, int name_width, int result_width)
{
printf("%*s: result %*llu ", name_width, e->name, result_width,
e->result.value);
if (e->result.running == e->result.enabled)
printf("running/enabled %llu\n", e->result.running);
else
printf("running %llu enabled %llu\n", e->result.running,
e->result.enabled);
}
void event_report(struct event *e)
{
event_report_justified(e, 0, 0);
}

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@ -0,0 +1,39 @@
/*
* Copyright 2013, Michael Ellerman, IBM Corp.
* Licensed under GPLv2.
*/
#ifndef _SELFTESTS_POWERPC_PMU_EVENT_H
#define _SELFTESTS_POWERPC_PMU_EVENT_H
#include <unistd.h>
#include <linux/perf_event.h>
#include "utils.h"
struct event {
struct perf_event_attr attr;
char *name;
int fd;
/* This must match the read_format we use */
struct {
u64 value;
u64 running;
u64 enabled;
} result;
};
void event_init(struct event *e, u64 config);
void event_init_named(struct event *e, u64 config, char *name);
void event_init_opts(struct event *e, u64 config, int type, char *name);
int event_open_with_options(struct event *e, pid_t pid, int cpu, int group_fd);
int event_open_with_group(struct event *e, int group_fd);
int event_open(struct event *e);
void event_close(struct event *e);
int event_reset(struct event *e);
int event_read(struct event *e);
void event_report_justified(struct event *e, int name_width, int result_width);
void event_report(struct event *e);
#endif /* _SELFTESTS_POWERPC_PMU_EVENT_H */

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@ -0,0 +1,46 @@
/*
* Copyright 2013, Michael Ellerman, IBM Corp.
* Licensed under GPLv2.
*/
.text
.global thirty_two_instruction_loop
.type .thirty_two_instruction_loop,@function
.section ".opd","aw",@progbits
thirty_two_instruction_loop:
.quad .thirty_two_instruction_loop, .TOC.@tocbase, 0
.previous
.thirty_two_instruction_loop:
cmpwi %r3,0
beqlr
addi %r4,%r3,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1
addi %r4,%r4,1 # 28 addi's
subi %r3,%r3,1
b .thirty_two_instruction_loop