From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 7 Aug 2000 10:55:58 -0700 (PDT) From: Matthew Dillon Message-Id: <200008071755.KAA01590@apollo.backplane.com> Subject: Re: RFC: design for new VM References: Sender: owner-linux-mm@kvack.org Return-Path: To: Alexander Viro Cc: Linus Torvalds , Rik van Riel , Chris Wedgwood , linux-mm@kvack.org, linux-kernel@vger.rutgers.edu List-ID: :> 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). Well... actually, a side effect of the FreeBSD buffer cache is to cache BMAP translations. What we do do, which kinda kills the cacheability aspects of balloc in some cases, is VOP_REALLOC() -- that is, the FFS filesystem will reallocate blocks to implement on-the-fly defragmentation. This typically occurs on writes. It works *very* well. This is a feature that actually used to be in FFS a few years ago but had to be turned off due to bugs. The bugs were fixed about a year ago and realloc was turned on by default in 4.x. -Matt Matthew Dillon -- 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/