[tip:perfcounters/core] perf top: Fall back to cpu-clock-tick hrtimer sampling if no cycle counter available

tip-bot for Ingo Molnar
2009-06-07T15:37:20Z

Commit-ID: 716c69fecacd42f2a304a97158e04af2786a3f65
Gitweb: http://git.kernel.org/tip/716c69fecacd42f2a304a97158e04af2786a3f65
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Sun, 7 Jun 2009 17:31:52 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sun, 7 Jun 2009 17:31:52 +0200

perf top: Fall back to cpu-clock-tick hrtimer sampling if no cycle counter available

On architectures/CPUs without PMU support but with perfcounters
enabled 'perf top' currently fails because it cannot create a
cycle based hw-perfcounter.

Fall back to the cpu-clock-tick sw-perfcounter in this case, which
is hrtimer based and will always work (as long as perfcounters
is enabled).

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
tools/perf/builtin-top.c | 113 +++++++++++++++++++++++++++------------------
tools/perf/util/usage.c | 10 ++--
2 files changed, 73 insertions(+), 50 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index fdc1d58..6da30a1 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -527,58 +527,81 @@ static void mmap_read(void)
}
}

-static int __cmd_top(void)
+int nr_poll;
+int group_fd;
+
+static void start_counter(int i, int counter)
{
struct perf_counter_attr *attr;
- pthread_t thread;
- int i, counter, group_fd, nr_poll = 0;
unsigned int cpu;
+
+ cpu = profile_cpu;
+ if (target_pid == -1 && profile_cpu == -1)
+ cpu = i;
+
+ attr = attrs + counter;
+
+ attr->sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_TID;
+ attr->freq = freq;
+
+try_again:
+ fd[i][counter] = sys_perf_counter_open(attr, target_pid, cpu, group_fd, 0);
+
+ if (fd[i][counter] < 0) {
+ int err = errno;
+
+ error("sys_perf_counter_open() syscall returned with %d (%s)\n",
+ fd[i][counter], strerror(err));
+
+ if (err == EPERM)
+ die(" No permission - are you root?\n");
+ /*
+ * If it's cycles then fall back to hrtimer
+ * based cpu-clock-tick sw counter, which
+ * is always available even if no PMU support:
+ */
+ if (attr->type == PERF_TYPE_HARDWARE
+ && attr->config == PERF_COUNT_CPU_CYCLES) {
+
+ warning(" ... trying to fall back to cpu-clock-ticks\n");
+ attr->type = PERF_TYPE_SOFTWARE;
+ attr->config = PERF_COUNT_CPU_CLOCK;
+ goto try_again;
+ }
+ exit(-1);
+ }
+ assert(fd[i][counter] >= 0);
+ fcntl(fd[i][counter], F_SETFL, O_NONBLOCK);
+
+ /*
+ * First counter acts as the group leader:
+ */
+ if (group && group_fd == -1)
+ group_fd = fd[i][counter];
+
+ event_array[nr_poll].fd = fd[i][counter];
+ event_array[nr_poll].events = POLLIN;
+ nr_poll++;
+
+ mmap_array[i][counter].counter = counter;
+ mmap_array[i][counter].prev = 0;
+ mmap_array[i][counter].mask = mmap_pages*page_size - 1;
+ mmap_array[i][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
+ PROT_READ, MAP_SHARED, fd[i][counter], 0);
+ if (mmap_array[i][counter].base == MAP_FAILED)
+ die("failed to mmap with %d (%s)\n", errno, strerror(errno));
+}
+
+static int __cmd_top(void)
+{
+ pthread_t thread;
+ int i, counter;
int ret;

for (i = 0; i < nr_cpus; i++) {
group_fd = -1;
- for (counter = 0; counter < nr_counters; counter++) {
-
- cpu = profile_cpu;
- if (target_pid == -1 && profile_cpu == -1)
- cpu = i;
-
- attr = attrs + counter;
-
- attr->sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_TID;
- attr->freq = freq;
-
- fd[i][counter] = sys_perf_counter_open(attr, target_pid, cpu, group_fd, 0);
- if (fd[i][counter] < 0) {
- int err = errno;
-
- error("syscall returned with %d (%s)\n",
- fd[i][counter], strerror(err));
- if (err == EPERM)
- printf("Are you root?\n");
- exit(-1);
- }
- assert(fd[i][counter] >= 0);
- fcntl(fd[i][counter], F_SETFL, O_NONBLOCK);
-
- /*
- * First counter acts as the group leader:
- */
- if (group && group_fd == -1)
- group_fd = fd[i][counter];
-
- event_array[nr_poll].fd = fd[i][counter];
- event_array[nr_poll].events = POLLIN;
- nr_poll++;
-
- mmap_array[i][counter].counter = counter;
- mmap_array[i][counter].prev = 0;
- mmap_array[i][counter].mask = mmap_pages*page_size - 1;
- mmap_array[i][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
- PROT_READ, MAP_SHARED, fd[i][counter], 0);
- if (mmap_array[i][counter].base == MAP_FAILED)
- die("failed to mmap with %d (%s)\n", errno, strerror(errno));
- }
+ for (counter = 0; counter < nr_counters; counter++)
+ start_counter(i, counter);
}

/* Wait for a minimal set of events before starting the snapshot */
diff --git a/tools/perf/util/usage.c b/tools/perf/util/usage.c
index 2cad286..e16bf9a 100644
--- a/tools/perf/util/usage.c
+++ b/tools/perf/util/usage.c
@@ -9,29 +9,29 @@ static void report(const char *prefix, const char *err, va_list params)
{
char msg[1024];
vsnprintf(msg, sizeof(msg), err, params);
- fprintf(stderr, "%s%s\n", prefix, msg);
+ fprintf(stderr, " %s%s\n", prefix, msg);
}

static NORETURN void usage_builtin(const char *err)
{
- fprintf(stderr, "\n usage: %s\n", err);
+ fprintf(stderr, "\n Usage: %s\n", err);
exit(129);
}

static NORETURN void die_builtin(const char *err, va_list params)
{
- report("fatal: ", err, params);
+ report(" Fatal: ", err, params);
exit(128);
}

static void error_builtin(const char *err, va_list params)
{
- report("error: ", err, params);
+ report(" Error: ", err, params);
}

static void warn_builtin(const char *warn, va_list params)
{
- report("warning: ", warn, params);
+ report(" Warning: ", warn, params);
}

/* If we are in a dlopen()ed .so write to a global variable would segfault