Date: Sat, 29 Nov 2003 12:16:58 +1100 From: Tim Robbins <tjr@freebsd.org> To: Dag-Erling Sm?rgrav <des@des.no> Cc: current@freebsd.org Subject: Re: Port of Niels Provos's file descriptor allocation code Message-ID: <20031129011658.GA1347@wombat.robbins.dropbear.id.au> In-Reply-To: <xzpvfp4816m.fsf@dwp.des.no> References: <20031127070239.GA12950@wombat.robbins.dropbear.id.au> <xzpvfp4816m.fsf@dwp.des.no>
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On Sat, Nov 29, 2003 at 01:32:01AM +0100, Dag-Erling Sm?rgrav wrote: > Tim Robbins <tjr@freebsd.org> writes: > > I've ported Niels Provos's file descriptor allocation code to FreeBSD > > in case anyone wants to try it out & run some benchmarks. If the performance > > boost turns out to be worth the added complexity, I might clean it up a > > bit and commit it. > > What exactly would be the point? If this is the OpenBSD fdalloc code, > recent widely-publicized benchmarks have shown it to be inferior to > ours. Perhaps you should concentrate on improving vm_map_find() and > vm_map_findspace() performance instead? It's also the NetBSD fdalloc code. They started with code similar to ours, in that it did a linear search of the file descriptor array to find an empty slot and used hints to speed up some common allocation patterns, then recently switched over to using the multi-level bitmap allocator. I can't think of any reason why we wouldn't see improvements similar to what they saw: http://www.citi.umich.edu/u/provos/benchmark/netbsd-fdalloc.jpg ... but I'm still working on benchmarking FreeBSD with & without the new allocator; I just posted the patch so that other people could experiment with it if they were interested. I don't plan on committing it until I have good evidence that it's an improvement over the current code. Tim
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