MINOR: activity: declare a new structure to collect per-function activity
The new sched_activity structure will be used to collect task-level
activity based on the target function. The principle is to declare a
large enough array to make collisions rare (256 entries), and hash
the function pointer using a reduced XXH to decide where to store the
stats. On first computation an entry is definitely assigned to the
array and it's done atomically. A special entry (0) is used to store
collisions ("others"). The goal is to make it easy and inexpensive for
the scheduler code to use these to store #calls, cpu_time and lat_time
for each task.
diff --git a/src/activity.c b/src/activity.c
index 79aad3e..0d64a36 100644
--- a/src/activity.c
+++ b/src/activity.c
@@ -27,6 +27,8 @@
/* One struct per thread containing all collected measurements */
struct activity activity[MAX_THREADS] __attribute__((aligned(64))) = { };
+/* One struct per function pointer hash entry (256 values, 0=collision) */
+struct sched_activity sched_activity[256] __attribute__((aligned(64))) = { };
/* Updates the current thread's statistics about stolen CPU time. The unit for
* <stolen> is half-milliseconds.