[PATCH xserver 0/3] Fix O(n*m) performance cliff in miarc

Keith Packard keithp at keithp.com
Wed Mar 1 23:20:57 UTC 2017

Adam Jackson <ajax at redhat.com> writes:

> So, way back in 946f664b, I removed a cache from the miarc code, with the
> justification that arcs were rare and the performance improvement wasn't
> worth it. I'd have been more right if the miarc code wasn't, what's the
> word, garbage.

Hey, that's some of my finest code from 1989 you're messing with...

> Rather than reintroduce the cache, this series holds on to the span data
> for the duration of a single pass through the arc. So we'll still compute
> things twice for double-dashed arcs, but that's still down in the "small
> numbers of milliseconds per arc in the worst case" regime.

Reviewed-by: Keith Packard <keithp at keithp.com>

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