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SubjectRe: [PATCH] mm: add resched points to remap_pmd_range/ioremap_pmd_range
On Thu, Jul 30, 2015 at 05:22:55PM +0200, Mike Galbraith wrote:
>
> I piddled about with the thought that it might be nice to be able to
> sprinkle cond_resched() about to cut rt latencies without wrecking
> normal load throughput, cobbled together a cond_resched_rt().
>
> On my little box that was a waste of time, as the biggest hits are block
> softirq and free_hot_cold_page_list().

Block softirq is one of our problems as well. It is a bit of a joke
that __do_softirq() moves work to ksoftirqd after 2ms, but block softirq
can take several 100ms in bad cases.

We could give individual softirqs a time budget. If they exceed the
budget they should complete, but reassert themselves. Not sure about
the rest, but that would be pretty simple to implement for block
softirq.

Jörn

--
Happiness isn't having what you want, it's wanting what you have.
-- unknown


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