diff options
Diffstat (limited to 'kernel/Documentation/arm/CCN.txt')
| -rw-r--r-- | kernel/Documentation/arm/CCN.txt | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/kernel/Documentation/arm/CCN.txt b/kernel/Documentation/arm/CCN.txt index 0632b3aad..ffca443a1 100644 --- 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. |