timers: split process wide cpu clocks/timers

Change the process wide cpu timers/clocks so that we:

 1) don't mess up the kernel with too many threads,
 2) don't have a per-cpu allocation for each process,
 3) have no impact when not used.

In order to accomplish this we're going to split it into two parts:

 - clocks; which can take all the time they want since they run
           from user context -- ie. sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID)

 - timers; which need constant time sampling but since they're
           explicity used, the user can pay the overhead.

The clock readout will go back to a full sum of the thread group, while the
timers will run of a global 'clock' that only runs when needed, so only
programs that make use of the facility pay the price.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 6 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index ea0ea1a4c36f..e752d973fa21 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -48,12 +48,11 @@ extern struct fs_struct init_fs;
         .posix_timers    = LIST_HEAD_INIT(sig.posix_timers),            \
         .cpu_timers     = INIT_CPU_TIMERS(sig.cpu_timers),              \
         .rlim           = INIT_RLIMITS,                                 \
-        .cputime        = { .totals = {                                 \
-                .utime = cputime_zero,                                  \
-                .stime = cputime_zero,                                  \
-                .sum_exec_runtime = 0,                                  \
-                .lock = __SPIN_LOCK_UNLOCKED(sig.cputime.totals.lock),  \
-        }, },                                                           \
+        .cputimer       = {                                             \
+                .cputime = INIT_CPUTIME,                                \
+                .running = 0,                                           \
+                .lock = __SPIN_LOCK_UNLOCKED(sig.cputimer.lock),        \
+        },                                                              \
 }
 
 extern struct nsproxy init_nsproxy;