mirror of https://gitee.com/openkylin/linux.git
53 lines
2.1 KiB
Plaintext
53 lines
2.1 KiB
Plaintext
|
ARM Cache Coherent Network
|
||
|
|
==========================
|
||
|
|
|
||
|
|
CCN-504 is a ring-bus interconnect consisting of 11 crosspoints
|
||
|
|
(XPs), with each crosspoint supporting up to two device ports,
|
||
|
|
so nodes (devices) 0 and 1 are connected to crosspoint 0,
|
||
|
|
nodes 2 and 3 to crosspoint 1 etc.
|
||
|
|
|
||
|
|
PMU (perf) driver
|
||
|
|
-----------------
|
||
|
|
|
||
|
|
The CCN driver registers a perf PMU driver, which provides
|
||
|
|
description of available events and configuration options
|
||
|
|
in sysfs, see /sys/bus/event_source/devices/ccn*.
|
||
|
|
|
||
|
|
The "format" directory describes format of the config, config1
|
||
|
|
and config2 fields of the perf_event_attr structure. The "events"
|
||
|
|
directory provides configuration templates for all documented
|
||
|
|
events, that can be used with perf tool. For example "xp_valid_flit"
|
||
|
|
is an equivalent of "type=0x8,event=0x4". Other parameters must be
|
||
|
|
explicitly specified. For events originating from device, "node"
|
||
|
|
defines its index. All crosspoint events require "xp" (index),
|
||
|
|
"port" (device port number) and "vc" (virtual channel ID) and
|
||
|
|
"dir" (direction). Watchpoints (special "event" value 0xfe) also
|
||
|
|
require comparator values ("cmp_l" and "cmp_h") and "mask", being
|
||
|
|
index of the comparator mask.
|
||
|
|
|
||
|
|
Masks are defined separately from the event description
|
||
|
|
(due to limited number of the config values) in the "cmp_mask"
|
||
|
|
directory, with first 8 configurable by user and additional
|
||
|
|
4 hardcoded for the most frequent use cases.
|
||
|
|
|
||
|
|
Cycle counter is described by a "type" value 0xff and does
|
||
|
|
not require any other settings.
|
||
|
|
|
||
|
|
Example of perf tool use:
|
||
|
|
|
||
|
|
/ # perf list | grep ccn
|
||
|
|
ccn/cycles/ [Kernel PMU event]
|
||
|
|
<...>
|
||
|
|
ccn/xp_valid_flit/ [Kernel PMU event]
|
||
|
|
<...>
|
||
|
|
|
||
|
|
/ # perf stat -C 0 -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \
|
||
|
|
sleep 1
|
||
|
|
|
||
|
|
The driver does not support sampling, therefore "perf record" will
|
||
|
|
not work. Also notice that only single cpu is being selected
|
||
|
|
("-C 0") - this is because perf framework does not support
|
||
|
|
"non-CPU related" counters (yet?) so system-wide session ("-a")
|
||
|
|
would try (and in most cases fail) to set up the same event
|
||
|
|
per each CPU.
|