On Fri, Dec 16, 2016 at 03:12:55PM -0800, Vikas Shivappa wrote:
+Continuous monitoring
+---------------------
+A new file cont_monitoring is added to perf_cgroup which helps to enable
+cqm continuous monitoring. Enabling this field would start monitoring of
+the cgroup without perf being launched. This can be used for long term
+light weight monitoring of tasks/cgroups.
+
+To enable continuous monitoring of cgroup p1.
+#echo 1 > /sys/fs/cgroup/perf_event/p1/perf_event.cqm_cont_monitoring
+
+To disable continuous monitoring of cgroup p1.
+#echo 0 > /sys/fs/cgroup/perf_event/p1/perf_event.cqm_cont_monitoring
+
+To read the counters at the end of monitoring perf can be used.
+
+LAZY and NOLAZY Monitoring
+--------------------------
+LAZY:
+By default when monitoring is enabled, the RMIDs are not allocated
+immediately and allocated lazily only at the first sched_in.
+There are 2-4 RMIDs per logical processor on each package. So if a dual
+package has 48 logical processors, there would be upto 192 RMIDs on each
+package = total of 192x2 RMIDs.
+There is a possibility that RMIDs can runout and in that case the read
+reports an error since there was no RMID available to monitor for an
+event.
+
+NOLAZY:
+When user wants guaranteed monitoring, he can enable the 'monitoring
+mask' which is basically used to specify the packages he wants to
+monitor. The RMIDs are statically allocated at open and failure is
+indicated if RMIDs are not available.
+
+To specify monitoring on package 0 and package 1:
+#echo 0-1 > /sys/fs/cgroup/perf_event/p1/perf_event.cqm_mon_mask
+
+An error is thrown if packages not online are specified.
I very much dislike both those for adding files to the perf cgroup.
Drivers should really not do that.
I absolutely hate the second because events already have affinity.
I can't see this happening.