Re: [PATCH] x86: Reduce the default HZ value

[H. Peter Anvin]

Peter Zijlstra wrote:
> The problem with scheduling a hrtimer along with tasks is that at high
> context switch rates the timer will never fire but you do pay the
> overhead of programming the hardware each time, something that can be
> about as expensive as the whole context switch itself.
>
> Although, I guess we could amortize that by not re-programming the timer
> when the existing timer is within a reasonable period (say 1ms) of the
> requested on.

That seems like a reasonable optimization since we're talking about 
multi-kHz context switch rates, here.

	-hpa

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