These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / Documentation / arm / CCN.txt

diff --git a/kernel/Documentation/arm/CCN.txt b/kernel/Documentation/arm/CCN.txt
index 0632b3a..ffca443 100644 (file)
--- a/kernel/Documentation/arm/CCN.txt
+++ b/kernel/Documentation/arm/CCN.txt
@@ -33,20 +33,23 @@ directory, with first 8 configurable by user and additional
 Cycle counter is described by a "type" value 0xff and does
 not require any other settings.
 
+The driver also provides a "cpumask" sysfs attribute, which contains
+a single CPU ID, of the processor which will be used to handle all
+the CCN PMU events. It is recommended that the user space tools
+request the events on this processor (if not, the perf_event->cpu value
+will be overwritten anyway). In case of this processor being offlined,
+the events are migrated to another one and the attribute is updated.
+
 Example of perf tool use:
 
 / # perf list | grep ccn
   ccn/cycles/                                        [Kernel PMU event]
 <...>
-  ccn/xp_valid_flit/                                 [Kernel PMU event]
+  ccn/xp_valid_flit,xp=?,port=?,vc=?,dir=?/          [Kernel PMU event]
 <...>
 
-/ # perf stat -C 0 -e ccn/cycles/,ccn/xp_valid_flit,xp=1,port=0,vc=1,dir=1/ \
+/ # perf stat -a -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.
+not work. Per-task (without "-a") perf sessions are not supported.