[PATCH v3] powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

[PATCH v3] powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

[Kajol Jain]

hv_24x7 performance monitoring unit creates list of supported events
from the event catalog obtained via HCALL. hv_24x7 catalog could also
contain invalid or dummy events with names like RESERVED*.
These events does not have any hardware counters backing them.
So patch adds a check to string compare the event names
to filter out them.

Result in power9 machine:

Before this patch:
.....
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/RESERVED_NEST1,chip=?/                     [Kernel PMU event]
  hv_24x7/RESERVED_NEST10,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST11,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST12,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST13,chip=?/                    [Kernel PMU event]
......

Dmesg:
[    0.000362] printk: console [hvc0] enabled
[    0.815452] hv-24x7: read 1530 catalog entries, created 537 event attrs
(0 failures), 275 descs

After this patch:
......
  hv_24x7/PM_XLINK2_OUT_ODD_AVLBL_CYC,chip=?/        [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/TOD,chip=?/                                [Kernel PMU event]
......

Demsg:
[    0.000357] printk: console [hvc0] enabled
[    0.808592] hv-24x7: read 1530 catalog entries, created 509 event attrs
(0 failures), 275 descs

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
---
 arch/powerpc/perf/hv-24x7.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

---
Changelog
v2 -> v3
- Removed "FREE_" check from "ignore_event".

v1 -> v2
- Include "RESERVED*" as part of the invalid event check as
  suggested by Madhavan Srinivasan
- Add new helper function "ignore_event" to check invalid/dummy
  events as suggested by Michael Ellerman
- Remove pr_info to print each invalid event as suggested by
  Michael Ellerman
---
diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index 6e7e820508df..2f32b532b359 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -764,6 +764,14 @@ static ssize_t catalog_event_len_validate(struct hv_24x7_event_data *event,
 	return ev_len;
 }
 
+/*
+ * Return true incase of invalid or dummy events with names like RESERVED*
+ */
+static bool ignore_event(const char *name)
+{
+	return (!strncmp(name, "RESERVED", 8)) ? true : false;
+}
+
 #define MAX_4K (SIZE_MAX / 4096)
 
 static int create_events_from_catalog(struct attribute ***events_,
@@ -894,6 +902,10 @@ static int create_events_from_catalog(struct attribute ***events_,
 
 		name = event_name(event, &nl);
 
+		if (ignore_event(name)) {
+			junk_events++;
+			continue;
+		}
 		if (event->event_group_record_len == 0) {
 			pr_devel("invalid event %zu (%.*s): group_record_len == 0, skipping\n",
 					event_idx, nl, name);
@@ -955,6 +967,9 @@ static int create_events_from_catalog(struct attribute ***events_,
 			continue;
 
 		name  = event_name(event, &nl);
+		if (ignore_event(name))
+			continue;
+
 		nonce = event_uniq_add(&ev_uniq, name, nl, event->domain);
 		ct    = event_data_to_attrs(event_idx, events + event_attr_ct,
 					    event, nonce);
-- 
2.27.0

Re: [PATCH v3] powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

[Michael Ellerman]

On Mon, 28 Dec 2020 14:22:04 +0530, Kajol Jain wrote:
> hv_24x7 performance monitoring unit creates list of supported events
> from the event catalog obtained via HCALL. hv_24x7 catalog could also
> contain invalid or dummy events with names like RESERVED*.
> These events does not have any hardware counters backing them.
> So patch adds a check to string compare the event names
> to filter out them.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events
      https://git.kernel.org/powerpc/c/e5f9d8858612c192a4326f39ed16c91c3a9e0893

cheers