Messages in this thread | | | From | David Woodhouse <> | Subject | Re: adjust prefetch in free_one_pgd() | Date | Sat, 03 Aug 2002 18:39:11 +0100 |
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torvalds@transmeta.com said: > My personal opinion is that if a prefetch has semantic meanings > outside the "speed up subsequent accesses", it should not be exposed > to the rest of the kernel (it might still be useful inside > architecture-specific routines like optimized memcpy etc).
Prefetch generally means 'bring it into the cache'. On architectures with non-cache-coherent DMA, doing a prefetch on wild address which happens to be a DMA buffer for which we've just said 'drop it from the cache' is generally a bad thing.
Not that I'm necessarily disagreeing with you -- but can you confirm that you are including all architectures with non-cache-coherent DMA in the 'broken hardware' category below, or point out what I'm missing?
> I'd rather speed up non-broken machines and let the broken hardware > hopefully slowly die away.
-- dwmw2
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