Re: [patch] sched: fix scheduling latencies for !PREEMPT kernels
From: Nick Piggin
Date: Tue Sep 14 2004 - 18:07:41 EST
Ingo Molnar wrote:
* Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
Another thing, I don't mean this to sound like a rhetorical question,
but if we have a preemptible kernel, why is it a good idea to sprinkle
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
cond_rescheds everywhere? Isn't this now the worst of both worlds? Why
would someone who really cares about latency not enable preempt?
two things:
1) none of the big distros enables CONFIG_PREEMPT in their kernels - not
even SuSE. This is pretty telling.
2) 10 new cond_resched()'s are not precisely 'sprinkle everywhere'.
No, but I mean putting them right down into fastpaths like the vmscan
one, for example.
And if I remember correctly, you resorted to putting them into
might_sleep as well (but I haven't read the code for a while, maybe
you're now getting decent results without doing that).
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