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>

6 files changed, 349 insertions, 1 deletions

diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
index b315740e4cd9..bd24ae5aaeab 100644
--- a/tools/testing/selftests/powerpc/Makefile
+++ b/tools/testing/selftests/powerpc/Makefile
@@ -13,7 +13,7 @@ CFLAGS := -Wall -O2 -flto -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(CUR
 
 export CC CFLAGS
 
-TARGETS =
+TARGETS = pmu
 
 endif
 
diff --git a/tools/testing/selftests/powerpc/pmu/Makefile b/tools/testing/selftests/powerpc/pmu/Makefile
new file mode 100644
index 000000000000..7216f0091655
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/Makefile
@@ -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
diff --git a/tools/testing/selftests/powerpc/pmu/count_instructions.c b/tools/testing/selftests/powerpc/pmu/count_instructions.c
new file mode 100644
index 000000000000..312b4f0fd27c
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/count_instructions.c
@@ -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");
+}
diff --git a/tools/testing/selftests/powerpc/pmu/event.c b/tools/testing/selftests/powerpc/pmu/event.c
new file mode 100644
index 000000000000..2b2d11df2450
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/event.c
@@ -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);
+}
diff --git a/tools/testing/selftests/powerpc/pmu/event.h b/tools/testing/selftests/powerpc/pmu/event.h
new file mode 100644
index 000000000000..e6993192ff34
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/event.h
@@ -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 */
diff --git a/tools/testing/selftests/powerpc/pmu/loop.S b/tools/testing/selftests/powerpc/pmu/loop.S
new file mode 100644
index 000000000000..8820e3df1444
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/loop.S
@@ -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