On Wed, Nov 11, 2020 at 6:01 AM Jiri Olsa [off-list ref] wrote:

On Fri, Nov 06, 2020 at 03:56:11PM -0600, Rob Herring wrote:

quoted

On Thu, Nov 5, 2020 at 4:41 PM Jiri Olsa [off-list ref] wrote:

quoted

On Thu, Nov 05, 2020 at 10:19:24AM -0600, Rob Herring wrote:

SNIP

quoted

quoted

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that maps page for each event, then perf_evsel__read
could go through the fast code, no?

No, because we're not self-monitoring (pid == 0 and cpu == -1). With
the following change:

diff --git a/tools/lib/perf/tests/test-evsel.c

b/tools/lib/perf/tests/test-evsel.c
index eeca8203d73d..1fca9c121f7c 100644

--- a/tools/lib/perf/tests/test-evsel.c
+++ b/tools/lib/perf/tests/test-evsel.c

@@ -17,6 +17,7 @@ static int test_stat_cpu(void)
 {
        struct perf_cpu_map *cpus;
        struct perf_evsel *evsel;
+       struct perf_event_mmap_page *pc;
        struct perf_event_attr attr = {
                .type   = PERF_TYPE_SOFTWARE,
                .config = PERF_COUNT_SW_CPU_CLOCK,

@@ -32,6 +33,15 @@ static int test_stat_cpu(void)
        err = perf_evsel__open(evsel, cpus, NULL);
        __T("failed to open evsel", err == 0);

+       pc = perf_evsel__mmap(evsel, 0);
+       __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

I'll need to check, I'm surprised this would depend on the way
you open the event

Any more thoughts on this?

sry I got stuck with other stuff.. I tried your change
and pc->cap_user_rdpmc is 0 because the test creates
software event, which does not support that

Sigh, yes, of course.

quoted

when I change that to:

        .type   = PERF_TYPE_HARDWARE,
        .config = PERF_COUNT_HW_CPU_CYCLES,

I don't see any of those warning you added

So I've now implemented the per fd mmap. It seems to run and get some
data, but for the above case the counts don't look right.

cpu0: count = 0x10883, ena = 0xbf42, run = 0xbf42
cpu1: count = 0x1bc65, ena = 0xa278, run = 0xa278
cpu2: count = 0x1fab2, ena = 0x91ea, run = 0x91ea
cpu3: count = 0x23d61, ena = 0x81ac, run = 0x81ac
cpu4: count = 0x2936a, ena = 0x7149, run = 0x7149
cpu5: count = 0x2cd4e, ena = 0x634f, run = 0x634f
cpu6: count = 0x3139f, ena = 0x53e7, run = 0x53e7
cpu7: count = 0x35350, ena = 0x4690, run = 0x4690

For comparison, this is what I get using the slow path read():
cpu0: count = 0x1c40, ena = 0x188b5, run = 0x188b5
cpu1: count = 0x18e0, ena = 0x1b8f4, run = 0x1b8f4
cpu2: count = 0x745e, ena = 0x1ab9e, run = 0x1ab9e
cpu3: count = 0x2416, ena = 0x1a280, run = 0x1a280
cpu4: count = 0x19c7, ena = 0x19b00, run = 0x19b00
cpu5: count = 0x1737, ena = 0x19262, run = 0x19262
cpu6: count = 0x11d0e, ena = 0x18944, run = 0x18944
cpu7: count = 0x20dbe, ena = 0x181f4, run = 0x181f4

hum, could you please send/push changes with that test?
I can try it and check

Here you go:

git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git user-perf-event-v5

Just comment out the mmap parts to get original behavior.

Rob

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