timers: Cache __next_timer_interrupt result

Each time a cpu goes to sleep on a NOHZ=y system the timer
wheel is searched for the next timer interrupt. It can take
quite a few cycles to find the next pending timer.

This patch adds a field to tvec_base that caches the result of
__next_timer_interrupt.

The hit ratio is around 80% on my thinkpad under normal use, on
a server I've seen hit ratios from 5% to 95% dependent on the
workload.

-v2: jiffies wrap fixes

Signed-off-by: Martin Schwidefsky <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: john stultz <[email protected]>
Cc: Venki Pallipadi <[email protected]>
LKML-Reference: <20090721202505.7d56a079@skybase>
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions