Re: page fault scalability patch V11 [0/7]: overview

Bill Davidsen
2004-11-22T18:06:03Z

Linus Torvalds wrote:
>
> On Sat, 20 Nov 2004, Nick Piggin wrote:
>
>>The per thread rss may wrap (maybe not 64-bit counters), but even so,
>>the summation over all threads should still end up being correct I
>>think.
>
>
> Yes. As long as the total rss fits in an int, it doesn't matter if any of
> them wrap. Addition is still associative in twos-complement arithmetic
> even in the presense of overflows.
>
> If you actually want to make it proper standard C, I guess you'd have to
> make the thing unsigned, which gives you the mod-2**n guarantees even if
> somebody were to ever make a non-twos-complement machine.

I think other stuff breaks as well, I think I saw you post some example
code using something like (a & -a) or similar within the last few
months. Fortunately neither 1's comp or BCD are likeliy to return in
hardware. Big-end vs. little-end is still an issue, though.

--
-bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me