Re: [pagevec] resize pagevec to O(lg(NR_CPUS))

[Nick Piggin]

Marcelo Tosatti wrote:
> > Sure. And when you fill it with pages, they'll use up 32KB of dcache
> > by using a single 64B line per page. Now that you've blown the cache,
> > when you go to move those pages to another list, you'll have to pull
> > them out of L2 again one at a time.
> >
> > OK, so a 511 item pagevec is pretty unlikely. How about a 64 item one
> > with 128 byte cachelines, and you're touching two cachelines per
> > page operation? That's 16K.
>
>
> Nick, 
>
> Note that you dont read/write data to the actual pages most of the 
> times pagevec's are used. The great majority is just page management code.  
> So we dont really blow the caches like you said.

You're often pulling them off lists though which is what will do it.
Not the actual page, but the struct page.

> I agree we need more tests :) 

Yep.

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