Re: Can and should the kernel HZ value be changed?

Stephen C. Tweedie (sct@redhat.com)
Sat, 9 Jan 1999 01:30:36 GMT


Hi,

On Tue, 5 Jan 1999 17:16:16 GMT, Egil Kvaleberg <egil@kvaleberg.no>
said:

> On 5 Jan 1999, MOLNAR Ingo wrote:
>> could you elaborate why it makes a difference?

> Pretty basal stuff, really: The more often you can switch context, the
> quicker the response will be for any given process residing down on the ready
> list somewhere. The is pretty vital for any real-timeish application, and
> nicely visualized and obvious (as well as gratifying for ones sanity) when
> running X.

This is not true. When we wake up a sleeping process, if that process
has a higher scheduling priority/credit than the current process, then
we reschedule _immediately_ (or rather, as soon as the interrupt or
syscall returns to user land). We do not wait for the next timer tick.
The value of HZ has nothing to do with the speed at which we respond to
such events!

--Stephen

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