diff options
Diffstat (limited to 'Documentation/arm')
| -rw-r--r-- | Documentation/arm/CCN.txt | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/Documentation/arm/CCN.txt b/Documentation/arm/CCN.txt index 0632b3aad83e..3a7604874762 100644 --- a/Documentation/arm/CCN.txt +++ b/Documentation/arm/CCN.txt @@ -33,6 +33,13 @@ 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 @@ -41,12 +48,8 @@ Example of perf tool use: 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/ \ +/ # 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. |