From e91895278b6da5898c188f565f2769eb7364dc22 Mon Sep 17 00:00:00 2001 From: Tony Lindgren Date: Thu, 7 Dec 2006 14:01:23 -0800 Subject: [PATCH 7/18] ARM: OMAP: Avoid updating system time for sub-jiffy interrupts Updating system time and reprogramming timer can cause latency issues on busy systems with lots of interrupts with constant updating of time and reprogramming the system timer. If a non-timer dyntick interrupt happens within a jiffy from the last interrupt, updating time and reprogramming the timer is unnecessary as we will get a timer interrupt soon anyways. Signed-off-by: Tony Lindgren --- arch/arm/plat-omap/timer32k.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) --- a/arch/arm/plat-omap/timer32k.c +++ b/arch/arm/plat-omap/timer32k.c @@ -219,6 +219,17 @@ static inline irqreturn_t _omap_32k_timer_interrupt(int irq, void *dev_id) static irqreturn_t omap_32k_timer_handler(int irq, void *dev_id) { + unsigned long now; + + now = omap_32k_sync_timer_read(); + + /* Don't bother reprogramming timer if last tick was before next + * jiffie. We will get another interrupt when previously programmed + * timer expires. This cuts down interrupt load quite a bit. + */ + if (now - omap_32k_last_tick < OMAP_32K_TICKS_PER_HZ) + return IRQ_HANDLED; + return _omap_32k_timer_interrupt(irq, dev_id); } -- 1.4.4.2