The patch titled
sched_clock: widen the max and min time
has been removed from the -mm tree. Its filename was
sched_clock-widen-the-max-and-min-time.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: sched_clock: widen the max and min time
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
With keeping the max and min sched time within one jiffy of the gtod clock
was too tight. Just before a schedule tick the max could easily be hit,
as well as just after a schedule_tick the min could be hit. This caused
the clock to jump around by a jiffy.
This patch widens the minimum to
last gtod + (delta_jiffies ? delta_jiffies - 1 : 0) * TICK_NSECS
and the maximum to
last gtod + (2 + delta_jiffies) * TICK_NSECS
This keeps the minum to gtod or if one jiffy less than delta jiffies and
the maxim 2 jiffies ahead of gtod. This may cause unstable TSCs to be a
bit more sporadic, but it helps keep a clock with a stable TSC working
well.
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched_clock.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff -puN kernel/sched_clock.c~sched_clock-widen-the-max-and-min-time kernel/sched_clock.c
--- a/kernel/sched_clock.c~sched_clock-widen-the-max-and-min-time
+++ a/kernel/sched_clock.c
@@ -96,14 +96,21 @@ static void __update_sched_clock(struct
s64 delta = now - scd->prev_raw;
WARN_ON_ONCE(!irqs_disabled());
- min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
+
+ min_clock = scd->tick_gtod +
+ (delta_jiffies ? delta_jiffies - 1 : 0) * TICK_NSEC;
if (unlikely(delta < 0)) {
clock++;
goto out;
}
- max_clock = min_clock + TICK_NSEC;
+ /*
+ * The clock must stay within a jiffie of the gtod.
+ * But since we may be at the start of a jiffy or the end of one
+ * we add another jiffy buffer.
+ */
+ max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC;
if (unlikely(clock + delta > max_clock)) {
if (clock < max_clock)
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
linux-next.patch
ftrace-disable-function-tracing-bringing-up-new-cpu.patch
split-the-typecheck-macros-out-of-include-linux-kernelh.patch
locking-add-typecheck-on-irqsave-and-friends-for-correct-flags.patch
locking-add-typecheck-on-irqsave-and-friends-for-correct-flags-fix.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
