RE: [PATCH] perf stat: Support per-cluster aggregation

[Chen, Tim C]

>
>From: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
>
>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 or imbalance.
>
>This patch adds 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
>[...]

Overall it looks good.  You can add my reviewed-by.

I wonder if we could enhance the help message 
in perf stat to tell user to refer to 
/sys/devices/system/cpu/cpuX/topology/*_id
to map relevant ids back to overall cpu topology.

For example the above example, cluster S56-D0-CLS158  has
really heavy load. It took me  a while
going through the code to figure out how to find
the info that maps cluster id to cpu.

Tim