From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 Aug 2000 22:17:46 -0400 (EDT) From: Alexander Viro Subject: Re: RFC: design for new VM In-Reply-To: <200008050152.SAA89298@apollo.backplane.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Matthew Dillon Cc: Linus Torvalds , Rik van Riel , Chris Wedgwood , linux-mm@kvack.org, linux-kernel@vger.rutgers.edu List-ID: On Fri, 4 Aug 2000, Matthew Dillon wrote: > :You have to have some page table locking mechanism for SMP eventually: I > :think you miss some of the problems because the current FreeBSD SMP stuff > :is mostly still "big kernel lock" (outdated info?), and you'll end up > :kicking yourself in a big way when you have the 300 processes sharing the > :same lock for that region.. > > If it were a long-held lock I'd worry, but if it's a lock on a pte > I don't think it can hurt. After all, even with separate page tables > if 300 processes fault on the same backing file offset you are going > to hit a bottleneck with MP locking anyway, just at a deeper level > (the filesystem rather then the VM system). Erm... I'm not sure about that - for one thing, you are not caching results of bmap(). We do. And our VFS is BKL-free, so contention really hits only on the VOP_BALLOC() level (that can be fixed too, but that's another story). -- 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.eu.org/Linux-MM/