On Mon, Aug 31, 2020 at 3:11 AM Jiri Olsa [off-list ref] wrote:

On Fri, Aug 28, 2020 at 02:56:10PM -0600, Rob Herring wrote:

SNIP

quoted

+int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count)
+{
+     struct perf_event_mmap_page *pc = map->base;
+     u32 seq, idx, time_mult = 0, time_shift = 0;
+     u64 cnt, cyc = 0, time_offset = 0, time_cycles = 0, time_mask = ~0ULL;
+
+     BUG_ON(!pc);
+
+     if (!pc->cap_user_rdpmc)
+             return -1;
+
+     do {
+             seq = READ_ONCE(pc->lock);
+             barrier();
+
+             count->ena = READ_ONCE(pc->time_enabled);
+             count->run = READ_ONCE(pc->time_running);
+
+             if (pc->cap_user_time && count->ena != count->run) {
+                     cyc = read_timestamp();
+                     time_mult = READ_ONCE(pc->time_mult);
+                     time_shift = READ_ONCE(pc->time_shift);
+                     time_offset = READ_ONCE(pc->time_offset);
+
+                     if (pc->cap_user_time_short) {
+                             time_cycles = READ_ONCE(pc->time_cycles);
+                             time_mask = READ_ONCE(pc->time_mask);
+                     }
+             }
+
+             idx = READ_ONCE(pc->index);
+             cnt = READ_ONCE(pc->offset);
+             if (pc->cap_user_rdpmc && idx) {

no need to check pc->cap_user_rdpmc again

I was thinking cap_user_rdpmc could change, but I guess idx will
always be 0 in that case.

quoted

+static int test_stat_user_read(int event)
+{
+     struct perf_counts_values counts = { .val = 0 };
+     struct perf_thread_map *threads;
+     struct perf_evsel *evsel;
+     struct perf_event_mmap_page *pc;
+     struct perf_event_attr attr = {
+             .type   = PERF_TYPE_HARDWARE,
+             .config = event,
+     };
+     int err, i;
+
+     threads = perf_thread_map__new_dummy();
+     __T("failed to create threads", threads);
+
+     perf_thread_map__set_pid(threads, 0, 0);
+
+     evsel = perf_evsel__new(&attr);
+     __T("failed to create evsel", evsel);
+
+     err = perf_evsel__open(evsel, NULL, threads);
+     __T("failed to open evsel", err == 0);
+
+     pc = perf_evsel__mmap(evsel);
+     __T("failed to mmap evsel", pc);
+
+#if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__)
+     __T("userspace counter access not supported", pc->cap_user_rdpmc);
+     __T("userspace counter access not enabled", pc->index);
+     __T("userspace counter width not set", pc->pmc_width >= 32);
+#endif
+
+     perf_evsel__read(evsel, 0, 0, &counts);
+     __T("failed to read value for evsel", counts.val != 0);
+
+     fputs("\n", stderr);
+     for (i = 0; i < 5; i++) {
+             volatile int count = 0x10000 << i;
+             __u64 start, end, last = 0;
+
+             fprintf(stderr, "\tloop = %u, ", count);

we should add support to display verbose output for tests,
because right now this breaks the output:

- running test-cpumap.c...OK
- running test-threadmap.c...OK
- running test-evlist.c...OK
- running test-evsel.c...
        loop = 65536, count = 328035
        loop = 131072, count = 655715
        loop = 262144, count = 1311075
        loop = 524288, count = 2627060
        loop = 1048576, count = 5253540

        loop = 65536, count = 327594
        loop = 131072, count = 659930
        loop = 262144, count = 1378892
        loop = 524288, count = 2664341
        loop = 1048576, count = 5365682
OK

but we can do it in separate change later

Would you like me to just comment this out then for now?

Rob

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