Re: [PATCH 2/3] higher order watermarks

[Nick Piggin <nickpiggin@yahoo.com.au>]

Marcelo Tosatti wrote:
> Hi Nick!
> 
> On Thu, Nov 04, 2004 at 11:20:54PM +1100, Nick Piggin wrote:
> 

>>So now what we need to do in order to calculate, say the amount of memory
>>that will satisfy order-2 *and above* (this is important) is the following:
>>
>>	z->free_pages - (order[0].nr_free << 0) - (order[1].nr_free << 1)
> 
> 
> Shouldnt that be then
> 
> free_pages -= z->free_area[o].nr_free << o;
> 
> instead of the current 
> 
> free_pages -= z->free_area[order].nr_free << o;
> 
> No?
> 

Yes, you're absolutely right. Sorry, this is what you were getting
at all along :P

> 
>>to find order-3 and above, you also need to subtract (order[2].nr_free << 
>>2).
>>
>>I quite liked this method because it has progressively less cost on lower
>>order allocations, and for order-0 we don't need to do any calculation.
> 
> 
> OK, now I get it. The only think which bugs me is the multiplication of 
> values with different meanings.
> 

Yeah it's wrong, of course. Good catch, thanks.

If you would care to send a patch Marcelo? I don't have a recent
-mm on hand at the moment. Would that be alright?

Thanks,
Nick
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