perf stat: Support per-cluster aggregation

Some platforms have 'cluster' topology and CPUs in the cluster will
share resources like L3 Cache Tag (for HiSilicon Kunpeng SoC) or L2
cache (for Intel Jacobsville). Currently parsing and building cluster
topology have been supported since [1].

perf stat has already supported aggregation for other topologies like
die or socket, etc. It'll be useful to aggregate per-cluster to find
problems like L3T bandwidth contention.

This patch add support for "--per-cluster" option for per-cluster
aggregation. Also update the docs and related test. The output will
be like:

[root@localhost tmp]# perf stat -a -e LLC-load --per-cluster -- sleep 5

 Performance counter stats for 'system wide':

S56-D0-CLS158    4      1,321,521,570      LLC-load
S56-D0-CLS594    4        794,211,453      LLC-load
S56-D0-CLS1030    4             41,623      LLC-load
S56-D0-CLS1466    4             41,646      LLC-load
S56-D0-CLS1902    4             16,863      LLC-load
S56-D0-CLS2338    4             15,721      LLC-load
S56-D0-CLS2774    4             22,671      LLC-load
[...]

On a legacy system without cluster or cluster support, the output will
be look like:
[root@localhost perf]# perf stat -a -e cycles --per-cluster -- sleep 1

 Performance counter stats for 'system wide':

S56-D0-CLS0   64         18,011,485      cycles
S7182-D0-CLS0   64         16,548,835      cycles

Note that this patch doesn't mix the cluster information in the outputs
of --per-core to avoid breaking any tools/scripts using it.

Note that perf recently supports "--per-cache" aggregation, but it's not
the same with the cluster although cluster CPUs may share some cache
resources. For example on my machine all clusters within a die share the
same L3 cache:
$ cat /sys/devices/system/cpu/cpu0/cache/index3/shared_cpu_list
0-31
$ cat /sys/devices/system/cpu/cpu0/topology/cluster_cpus_list
0-3

[1] commit c5e22feffdd7 ("topology: Represent clusters of CPUs within a die")

Tested-by: Jie Zhan <zhanjie9@hisilicon.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Cc: james.clark@arm.com
Cc: 21cnbao@gmail.com
Cc: prime.zeng@hisilicon.com
Cc: Jonathan.Cameron@huawei.com
Cc: fanghao11@huawei.com
Cc: linuxarm@huawei.com
Cc: tim.c.chen@intel.com
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240208024026.2691-1-yangyicong@huawei.com

1 files changed, 11 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 5af2e432b54f..29756a87ab6f 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -308,6 +308,14 @@ use --per-die in addition to -a. (system-wide).  The output includes the
 die number and the number of online processors on that die. This is
 useful to gauge the amount of aggregation.
 
+--per-cluster::
+Aggregate counts per processor cluster for system-wide mode measurement.  This
+is a useful mode to detect imbalance between clusters.  To enable this mode,
+use --per-cluster in addition to -a. (system-wide).  The output includes the
+cluster number and the number of online processors on that cluster. This is
+useful to gauge the amount of aggregation. The information of cluster ID and
+related CPUs can be gotten from /sys/devices/system/cpu/cpuX/topology/cluster_{id, cpus}.
+
 --per-cache::
 Aggregate counts per cache instance for system-wide mode measurements.  By
 default, the aggregation happens for the cache level at the highest index
@@ -396,6 +404,9 @@ Aggregate counts per processor socket for system-wide mode measurements.
 --per-die::
 Aggregate counts per processor die for system-wide mode measurements.
 
+--per-cluster::
+Aggregate counts perf processor cluster for system-wide mode measurements.
+
 --per-cache::
 Aggregate counts per cache instance for system-wide mode measurements.  By
 default, the aggregation happens for the cache level at the highest index