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author | Steven Rostedt <rostedt@goodmis.org> | 2008-07-07 14:16:51 -0400 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-07-11 15:53:25 +0200 |
commit | f7cce27f5605b9e137b829a47949cb2d3c7e1cab (patch) | |
tree | fbe270ccfb5cee3d055a52b6351ade2d34c5d74b /kernel/sched_clock.c | |
parent | 62c43dd9864dbd52ff158922d1d08c75f20335af (diff) | |
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sched_clock: widen the max and min time
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@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_clock.c')
-rw-r--r-- | kernel/sched_clock.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index e383bc7..42b81fa 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -96,14 +96,21 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now) 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) |