On 6/21/05, Lee Revell <[email protected]> wrote:
> On Mon, 2005-06-20 at 23:54 -0700, Andrew Morton wrote:
> > CONFIG_HZ for x86 and ia64: changes default HZ to 250, make HZ
> > Kconfigurable.
> >
> > Will merge (will switch default to 1000 Hz later if that seems
> > necessary)
>
> Are you serious? You're changing the *default* HZ in a stable kernel
> series?!?
>
> This is a big regression, it degrades the resolution of system calls.
Not that my opinion should sway anybody else, but I really would
prefer more of the in-kernel sleep callers were converted to use
human-time units (and thus were verified to be correct) so that
switching HZ will result in the *same* latencies. How much of moving
to lower HZ values is due to the fact that everything is request 10ms
for 1 jiffy of sleep instead of 1 ms? It's hard to tell if the gain is
there or from the lower frequency of interrupts.
I've sent out a lot of patches in this direction (using msleep() and
msleep_interruptible() and my soft-timer rework on top of John
Stultz's timeofday rework converts the entire soft-timer subsystem to
use human-time instead of jiffies as it's unit of expiration), but
there is still *a lot* of work left to do :( I will keep sending
patches, but am being pulled in other directions currently.
Just my $.02.
Thanks,
Nish
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