Date: Tue, 03 Jun 2003 17:33:00 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Paul Richards <paul@freebsd-services.com> Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: VFS: C99 sparse format for struct vfsops Message-ID: <XFMail.20030603173300.jhb@FreeBSD.org> In-Reply-To: <1054586934.1388.4.camel@cf.freebsd-services.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 02-Jun-2003 Paul Richards wrote: > On Mon, 2003-06-02 at 21:04, Paul Richards wrote: > >> >> The tradeoff with using an index into an array is that there'd be a >> heavy penalty for growing the array if an extra method didn't fit, but >> that would be exceptionally rare and with our present usage we'd never >> have that happen. > > I'm not sure this is actually a problem after all since the Interface > doesn't change and therefore we know a-priori how many methods there can > be so we can pre-allocate an array. I wonder why Doug didn't do this, > perhaps he thought that there'd be very large interfaces and 255 was a > reasonable compromise for a cache. However, in practice we'd save a lot > of space per kobj by preallocating the actual number of entries we > needed for the Interface instead and then we could do away with the _ce > problem. This would actually speed up the dispatch a lot too since we > wouldn't have to traverse a list looking for a matching method entry and > could call the function directly from the method table. > > Doug, am I missing something? Well, it's dfr@ rather than doug@ :) (dfr@ cc'd) -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?XFMail.20030603173300.jhb>