Re: [PATCH 1/3] dynticks - implement no idle hz for x86

[Tony Lindgren <tony@atomide.com>]

* Nishanth Aravamudan <nacc@us.ibm.com> [050906 23:55]:

...

> Sigh, later than I had hoped, but here is what I have hashed out so far.
> Does it seem like a step in the right direction? Rather hand-wavy, but I
> think it's mostly correct ;)

Some comments below.

> - include/linux/intsource.h
> 	with definitions in kernel/intsource.c
> 
> #define DYN_TICK_ENABLED	(1 << 1)
> #define DYN_TICK_SUITABLE	(1 << 0)
> 
> #define DYN_TICK_MIN_SKIP	2
> 
> /* Abstraction of an interrupt source
>  * @state: current state
>  * @max_skip: current maximum number of ticks to skip
>  * @arch_init: initialization routine
>  * @arch_enable_dyn_tick: called via sysfs to enable interrupt skipping
>  * @arch_disable_dyn_tick: called via sysfs to disable interrupt
>  * 				skipping
>  * @arch_set_all_cpus_idle: last cpu to go idle calls this, which should
>  * 				disable any timesource (e.g. PIT on x86)
>  * @arch_recover_time: handler for returning from skipped ticks and keeping
>  * 				time consistent
>  */
> struct interrupt_source {
> 	unsigned int state;
> 	unsigned long max_skip;
> 	int (*arch_init) (void);
> 	void (*arch_enable_dyn_tick) (void);
> 	void (*arch_disable_dyn_tick) (void);
> 	unsigned long (*arch_reprogram) (unsigned long); /* return number of ticks skipped */
> 	unsigned long (*arch_recover_time) (int, void *, struct pt_regs *); /* handler in arm */
> 	/* following empty in UP */
> 	void (*arch_set_all_cpus_idle) (int);
> 	spinlock_t lock;
> };

I would still call the struct dyntick, have CONFIG_DYNTICK, and then have
CONFIG_NO_IDLE_HZ and possibly CONFIG_SUBJIFFIE_TIMER register to use it
like I said in my earlier mail. Would that solve the issues you have
with the naming?

> /* return number of ticks skipped, potentially for accounting purposes? */
> extern unsigned long reprogram_interrupt(void);

The number of ticks skipped can be potentially used in idle loops to
select which ACPI C state to go to depending on the estimated length of
sleep.

Regards,
 
Tony