Re: [PATCH] 1/6: 64 bit jiffies

[Tim Schmielau]

On Sat, 11 May 2002, Denis Vlasenko wrote:

> On 11 May 2002 08:25, Tim Schmielau wrote:
> > +static inline void init_jiffieswrap_timer(void)
> > +{
> > +	init_timer(&jiffieswrap_timer);
> > +	jiffieswrap_timer.expires = jiffies + CHECK_JIFFIESWRAP_INTERVAL;
> > +	jiffieswrap_timer.function = check_jiffieswrap;
> > +	add_timer(&jiffieswrap_timer);
> > +}
> 
> I'm ignorant on the issue... does active timer mandate check for
> expiration at every timer tick? 

No, timers are implemented in a highly efficient manner. The above
timer will just add O(1) cost to 4 table refills, meaning some 100 cycles 
per quarter of a year.

> If yes, it is somewhat silly to use timer:
> such check would be more costly than
> 	
> 	if(!++jiffies) jiffies_hi++;
> 
> (or similar) construct in timer int.
> 
> BTW, I always liked above thing more that any other 64 jiffy solution.
> What's wrong with it?

It's slower than

	jiffies_64++;

which went into Linus' tree yesterday :-)

Tim