sched clock: revert various sched_clock() changes

Found an interactivity problem on a quad core test-system - simple
CPU loops would occasionally delay the system un an unacceptable way.

After much debugging with Peter Zijlstra it turned out that the problem
is caused by the string of sched_clock() changes - they caused the CPU
clock to jump backwards a bit - which confuses the scheduler arithmetics.

(which is unsigned for performance reasons)

So revert:

 # c300ba2: sched_clock: and multiplier for TSC to gtod drift
 # c0c8773: sched_clock: only update deltas with local reads.
 # af52a90: sched_clock: stop maximum check on NO HZ
 # f7cce27: sched_clock: widen the max and min time

This solves the interactivity problems.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>

1 files changed, 0 insertions, 2 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 825b4c00fe44..f5da526424a9 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -289,7 +289,6 @@ void tick_nohz_stop_sched_tick(int inidle)
                         ts->tick_stopped = 1;
                         ts->idle_jiffies = last_jiffies;
                         rcu_enter_nohz();
-                        sched_clock_tick_stop(cpu);
                 }
 
                 /*
@@ -392,7 +391,6 @@ void tick_nohz_restart_sched_tick(void)
         select_nohz_load_balancer(0);
         now = ktime_get();
         tick_do_update_jiffies64(now);
-        sched_clock_tick_start(cpu);
         cpu_clear(cpu, nohz_cpu_mask);
 
         /*