commit 4cd4c1b40d40447fb5e7ba80746c6d7ba91d7a53
author Peter Zijlstra <a.p.zijlstra@chello.nl> Thu Feb 05 12:24:16 2009 +0100
committer Ingo Molnar <mingo@elte.hu> Thu Feb 05 13:04:33 2009 +0100
tree b1e580d5284648d6884e951d995509094a92cca4
parent 32bd671d6cbeda60dc73be77fa2b9037d9a9bfa0

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>

kernel/itimer.c

diff --git a/kernel/itimer.c b/kernel/itimer.c
index 6a5fe93..58762f7 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -62,7 +62,7 @@
 			struct task_cputime cputime;
 			cputime_t utime;
 
-			thread_group_cputime(tsk, &cputime);
+			thread_group_cputimer(tsk, &cputime);
 			utime = cputime.utime;
 			if (cputime_le(cval, utime)) { /* about to fire */
 				cval = jiffies_to_cputime(1);
@@ -82,7 +82,7 @@
 			struct task_cputime times;
 			cputime_t ptime;
 
-			thread_group_cputime(tsk, &times);
+			thread_group_cputimer(tsk, &times);
 			ptime = cputime_add(times.utime, times.stime);
 			if (cputime_le(cval, ptime)) { /* about to fire */
 				cval = jiffies_to_cputime(1);