From: Tony Lindgren Date: Thu, 7 Dec 2006 22:01:23 +0000 (-0800) Subject: ARM: OMAP: Avoid updating system time for sub-jiffy interrupts X-Git-Tag: v2.6.21-omap1~30^2~78 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=4e97745f1a37b8a71e8faaae70cebe6ac42818bc;p=linux-2.6-omap-h63xx.git 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 --- diff --git a/arch/arm/plat-omap/timer32k.c b/arch/arm/plat-omap/timer32k.c index 26531060116..c37d7b41183 100644 --- 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); }