> > across many OSes. On the other hand, Apache in particular may not
> > access enough memory to make a huge difference.
>
> Remember, this is TLB flushes, not cache flushes, we're talking about.
> *Every* memory access after a TLB flush needs to reload the TLB, even if
> it is just a read from already-cached memory. Even just spinning in
> kernel space may require TLB refills after a flush (although newer
> Pentia do let you mark certain page tables as global, so a mm replace
> won't evict those TLBs).
yes and this is a pretty important effect. Also, a TLB miss on a Xeon with
all the page table info cached takes 3 cycles (and does not cause a
pipeline stall, so the real cost can be lower than this). So the cost for
a TLB flush is not all that high as it seems at first sight.
-- mingo
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