[PATCH v3 12/15] perf mem/c2c: Add load store event mappings for AMD

Ravi Bangoria
2022-09-28T10:02:43Z

Perf mem and c2c tools are wrappers around perf record with mem load/
store events. IBS tagged load/store sample provides most of the
information needed for these tools. Wire in ibs_op// event as mem-ldst
event for AMD.

There are some limitations though: Only load/store micro-ops provide
mem/c2c information. Whereas, IBS does not have a way to choose a
particular type of micro-op to tag. This results in many non-LS
micro-ops being tagged which appear as N/A in the perf report. IBS,
being an uncore pmu from kernel point of view[1], does not support per
process monitoring. Thus, perf mem/c2c on AMD are currently supported
in per-cpu mode only.

Example:
$ sudo ./perf mem record -- -c 10000
^C[ perf record: Woken up 227 times to write data ]
[ perf record: Captured and wrote 58.760 MB perf.data (836978 samples) ]

$ sudo ./perf mem report -F mem,sample,snoop
Samples: 836K of event 'ibs_op//', Event count (approx.): 8418762
Memory access Samples Snoop
N/A 700620 N/A
L1 hit 126675 N/A
L2 hit 424 N/A
L3 hit 664 HitM
L3 hit 10 N/A
Local RAM hit 2 N/A
Remote RAM (1 hop) hit 8558 N/A
Remote Cache (1 hop) hit 3 N/A
Remote Cache (1 hop) hit 2 HitM
Remote Cache (2 hops) hit 10 HitM
Remote Cache (2 hops) hit 6 N/A
Uncached hit 4 N/A

[1]: https://lore.kernel.org/lkml/20220829113347.295-1-ravi.bangoria@amd.com

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/Documentation/perf-c2c.txt | 14 ++++++++----
tools/perf/Documentation/perf-mem.txt | 3 ++-
tools/perf/arch/x86/util/mem-events.c | 31 +++++++++++++++++++++++++--
3 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/tools/perf/Documentation/perf-c2c.txt b/tools/perf/Documentation/perf-c2c.txt
index f1f7ae6b08d1..5c5eb2def83e 100644
--- a/tools/perf/Documentation/perf-c2c.txt
+++ b/tools/perf/Documentation/perf-c2c.txt
@@ -19,9 +19,10 @@ C2C stands for Cache To Cache.
The perf c2c tool provides means for Shared Data C2C/HITM analysis. It allows
you to track down the cacheline contentions.

-On x86, the tool is based on load latency and precise store facility events
+On Intel, the tool is based on load latency and precise store facility events
provided by Intel CPUs. On PowerPC, the tool uses random instruction sampling
-with thresholding feature.
+with thresholding feature. On AMD, the tool uses IBS op pmu (due to hardware
+limitations, perf c2c is not supported on Zen3 cpus).

These events provide:
- memory address of the access
@@ -49,7 +50,8 @@ RECORD OPTIONS

-l::
--ldlat::
- Configure mem-loads latency. (x86 only)
+ Configure mem-loads latency. Supported on Intel and Arm64 processors
+ only. Ignored on other archs.

-k::
--all-kernel::
@@ -135,11 +137,15 @@ Following perf record options are configured by default:
-W,-d,--phys-data,--sample-cpu

Unless specified otherwise with '-e' option, following events are monitored by
-default on x86:
+default on Intel:

cpu/mem-loads,ldlat=30/P
cpu/mem-stores/P

+following on AMD:
+
+ ibs_op//
+
and following on PowerPC:

cpu/mem-loads/
diff --git a/tools/perf/Documentation/perf-mem.txt b/tools/perf/Documentation/perf-mem.txt
index 66177511c5c4..005c95580b1e 100644
--- a/tools/perf/Documentation/perf-mem.txt
+++ b/tools/perf/Documentation/perf-mem.txt
@@ -85,7 +85,8 @@ RECORD OPTIONS
Be more verbose (show counter open errors, etc)

--ldlat <n>::
- Specify desired latency for loads event. (x86 only)
+ Specify desired latency for loads event. Supported on Intel and Arm64
+ processors only. Ignored on other archs.

In addition, for report all perf report options are valid, and for record
all perf record options.
diff --git a/tools/perf/arch/x86/util/mem-events.c b/tools/perf/arch/x86/util/mem-events.c
index 5214370ca4e4..f683ac702247 100644
--- a/tools/perf/arch/x86/util/mem-events.c
+++ b/tools/perf/arch/x86/util/mem-events.c
@@ -1,7 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
#include "util/pmu.h"
+#include "util/env.h"
#include "map_symbol.h"
#include "mem-events.h"
+#include "linux/string.h"

static char mem_loads_name[100];
static bool mem_loads_name__init;
@@ -12,18 +14,43 @@ static char mem_stores_name[100];

#define E(t, n, s) { .tag = t, .name = n, .sysfs_name = s }

-static struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX] = {
+static struct perf_mem_event perf_mem_events_intel[PERF_MEM_EVENTS__MAX] = {
E("ldlat-loads", "%s/mem-loads,ldlat=%u/P", "%s/events/mem-loads"),
E("ldlat-stores", "%s/mem-stores/P", "%s/events/mem-stores"),
E(NULL, NULL, NULL),
};

+static struct perf_mem_event perf_mem_events_amd[PERF_MEM_EVENTS__MAX] = {
+ E(NULL, NULL, NULL),
+ E(NULL, NULL, NULL),
+ E("mem-ldst", "ibs_op//", "ibs_op"),
+};
+
+static int perf_mem_is_amd_cpu(void)
+{
+ struct perf_env env = { .total_mem = 0, };
+
+ perf_env__cpuid(&env);
+ if (env.cpuid && strstarts(env.cpuid, "AuthenticAMD"))
+ return 1;
+ return -1;
+}
+
struct perf_mem_event *perf_mem_events__ptr(int i)
{
+ /* 0: Uninitialized, 1: Yes, -1: No */
+ static int is_amd;
+
if (i >= PERF_MEM_EVENTS__MAX)
return NULL;

- return &perf_mem_events[i];
+ if (!is_amd)
+ is_amd = perf_mem_is_amd_cpu();
+
+ if (is_amd == 1)
+ return &perf_mem_events_amd[i];
+
+ return &perf_mem_events_intel[i];
}

bool is_mem_loads_aux_event(struct evsel *leader)
--
2.31.1