From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Date: Mon, 22 Nov 2004 18:06:03 +0000 Subject: Re: page fault scalability patch V11 [0/7]: overview Message-Id: <41A22A8B.8050703@tmr.com> List-Id: References: <419E98E7.1080402@yahoo.com.au> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Linus Torvalds Cc: Nick Piggin , Christoph Lameter , akpm@osdl.org, Hugh Dickins , linux-mm@kvack.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org 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