Re: [patch] Performance Counters for Linux, v3

William Cohen
2008-12-11T22:05:22Z

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I was taking a look at the proposed performance monitoring and kerneltop.c. I
noticed that http://redhat.com/~mingo/perfcounters/kerneltop.c doesn't work
with the v3 version. I didn't see a more recent version available, so I made
some modifications to make allow it to work with the v3 kernel (with the
attached). However, I assume some where there is an updated version of kerneltop.c

The Documentation/perf-counters.txt doesn't describe how the group_fd is used.
Found that -1 used to indicate not connected to any other fd.

-Will

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--- kerneltop.c.old 2008-12-11 15:34:58.000000000 -0500
+++ kerneltop.c 2008-12-11 16:06:28.000000000 -0500
@@ -62,15 +62,31 @@
# define __NR_perf_counter_open 333
#endif

+/*
+ * Hardware event to monitor via a performance monitoring counter:
+ */
+struct perf_counter_hw_event {
+ int64_t type;
+
+ u_int64_t irq_period;
+ u_int32_t record_type;
+
+ u_int32_t disabled : 1, /* off by default */
+ nmi : 1, /* NMI sampling */
+ raw : 1, /* raw event type */
+ __reserved_1 : 29;
+
+ u_int64_t __reserved_2;
+};
+
int
-perf_counter_open(int hw_event_type,
- unsigned int hw_event_period,
- unsigned int record_type,
+perf_counter_open(struct perf_counter_hw_event *hw_event_uptr,
pid_t pid,
- int cpu)
+ int cpu,
+ int group_fd)
{
- return syscall(__NR_perf_counter_open, hw_event_type, hw_event_period,
- record_type, pid, cpu);
+ return syscall(__NR_perf_counter_open, hw_event_uptr,
+ pid, cpu, group_fd);
}

enum hw_event_types {
@@ -82,10 +98,6 @@
PERF_COUNT_BRANCH_MISSES,
PERF_COUNT_MAX,

- /*
- * If this bit is set in the type, then trigger NMI sampling:
- */
- PERF_COUNT_NMI = (1 << 30),
};

const char *event_types [] = {
@@ -616,14 +628,14 @@
{
struct pollfd event_array[MAX_NR_CPUS][MAX_COUNTERS];
int fd[MAX_NR_CPUS][MAX_COUNTERS];
- unsigned int nmi_flag = 0;
- unsigned int flags, cpu;
+ unsigned int cpu;
int i, counter;
uint64_t ip;
ssize_t res;
#if USE_POLL
int ret;
#endif
+ struct perf_counter_hw_event hw_event;

process_options(argc, argv);

@@ -633,18 +645,18 @@

assert(nr_cpus <= MAX_NR_CPUS);

- if (nmi)
- nmi_flag |= PERF_COUNT_NMI;
-
for (i = 0; i < nr_cpus; i++) {
for (counter = 0; counter < nr_counters; counter++) {
- flags = event_id[counter] | nmi_flag;
-
cpu = profile_cpu;
if (tid == -1 && profile_cpu == -1)
cpu = i;
-
- fd[i][counter] = perf_counter_open(flags, event_count[counter], 1, tid, cpu);
+ hw_event.type = event_id[counter];
+ hw_event.irq_period = event_count[counter];
+ hw_event.record_type = 1;
+ hw_event.nmi = nmi ? 1 : 0;
+
+ fd[i][counter] = perf_counter_open(&hw_event, tid,
+ cpu, -1 );
if (fd[i][counter] < 0) {
printf("kerneltop error: syscall returned with %d (%s)\n",
fd[i][counter], strerror(-fd[i][counter]));