From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 27 Dec 2002 12:18:23 -0800 (PST) From: Linus Torvalds Subject: Re: shared pagetable benchmarking In-Reply-To: <47580000.1041020194@[10.1.1.5]> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Daniel Phillips , Andrew Morton , linux-mm@kvack.org List-ID: On Fri, 27 Dec 2002, Dave McCracken wrote: > > I gave Andrew a patch that does make it break even on small forks, by doing > the copy at fork time when a process only has 3 pte pages. My tests > indicate that any process with 4 or more pte pages usually is faster by > doing the share. Ok, so it doesn't actually break even, it just disables itself. That's not the same thing in my book, but may of course be acceptable. I'd personally be much happier if just the real cause for the rmap slowdown was fixed, possibly by having it be done lazily (the shared page table stuff tries to do the _copy_ of the rmap information lazily, but maybe the real solution is to go one level further and just set the dang things up lazily in the first place, since most of the time it's not even needed). That's clearly not 2.6.x material. But at this point I doubt that shared page tables are either, unless they fix something more important than fork() speed for processes that are larger than 16MB. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/