Date: Tue, 10 Nov 1998 10:14:02 -0800 From: Mike Smith <mike@smith.net.au> To: Alfred Perlstein <bright@hotjobs.com> Cc: current@FreeBSD.ORG Subject: Re: Simple NFS ACCESS caching, call for testers Message-ID: <199811101814.KAA03982@dingo.cdrom.com> In-Reply-To: Your message of "Tue, 10 Nov 1998 12:48:55 EST." <Pine.BSF.4.05.9811101214590.370-100000@porkfriedrice.ny.genx.net>
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> > vfs.nfs.access_cache_timeout: 6 > vfs.nfs.access_cache_hits: 225001 > vfs.nfs.access_cache_fills: 10981 About a 95% hit rate, or a saving of about 450,000 packets on the network. Your tests are a close-to-ideal case in that there's only one user so the cache entry in the vnode won't get thrashed, but even so this is much better than I'd expected. > I'm trying to figure out some sorta test that would stress the cache but > couldn't think of anything besides the two I just ran. The "worst case" scenario for this scheme is multiple users (literally, multiple different sets of credentials) accessing the same set of files at once. Because the ACCESS status is a 3-tuple of path, credentials and rights, caching them "properly" is very expensive. The current approach is very cheap, but I expect it will degrade substantially under this sort of load. It also doesn't preserve state across multiple disconnected accesses to the same file (unless nfsnodes are cached and reused, I'm not sure about this). Still, as I said it's cheap, and it seems to offer some significant improvements. It can probably also be retrofitted to 2.2, which will make some of our heavy NFS customers happy. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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