Date: Mon, 12 Nov 2012 22:23:48 -0800 From: Peter Wemm <peter@wemm.org> To: Alfred Perlstein <bright@mu.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Adrian Chadd <adrian@freebsd.org> Subject: Re: auto tuning tcp Message-ID: <CAGE5yCoj1dL9w-EMMi8iYMTOq9uUUHmFg4rMY7aPneUBHBv67Q@mail.gmail.com> In-Reply-To: <50A1E47C.1030208@mu.org> References: <50A0A0EF.3020109@mu.org> <50A0A502.1030306@networx.ch> <50A0B8DA.9090409@mu.org> <50A0C0F4.8010706@networx.ch> <EB2C22B5-C18D-4AC2-8694-C5C0D96C07B3@mu.org> <50A13961.1030909@networx.ch> <50A14460.9020504@mu.org> <50A1E2E7.3090705@mu.org> <50A1E47C.1030208@mu.org>
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On Mon, Nov 12, 2012 at 10:11 PM, Alfred Perlstein <bright@mu.org> wrote: > On 11/12/12 10:04 PM, Alfred Perlstein wrote: >> >> On 11/12/12 10:48 AM, Alfred Perlstein wrote: >>> >>> On 11/12/12 10:01 AM, Andre Oppermann wrote: >>>> >>>> >>>> I've already added the tunable "kern.maxmbufmem" which is in pages. >>>> That's probably not very convenient to work with. I can change it >>>> to a percentage of phymem/kva. Would that make you happy? >>>> >>> >>> It really makes sense to have the hash table be some relation to sockets >>> rather than buffers. >>> >>> If you are hashing "foo-objects" you want the hash to be some relation to >>> the max amount of "foo-objects" you'll see, not backwards derived from the >>> number of "bar-objects" that "foo-objects" contain, right? >>> >>> Because we are hashing the sockets, right? not clusters. >>> >>> Maybe I'm wrong? I'm open to ideas. >> >> >> Hey Andre, the following patch is what I was thinking >> (uncompiled/untested), it basically rounds up the maxsockets to a power of 2 >> and replaces the default 512 tcb hashsize. >> >> It might make sense to make the auto-tuning default to a minimum of 512. >> >> There are a number of other hashes with static sizes that could make use >> of this logic provided it's not upside-down. >> >> Any thoughts on this? >> >> Tune the tcp pcb hash based on maxsockets. >> Be more forgiving of poorly chosen tunables by finding a closer power >> of two rather than clamping down to 512. >> Index: tcp_subr.c >> =================================================================== > > > Sorry, GUI mangled the patch... attaching a plain text version. > > Wait, you want to replace a hash with a flat array? Why even bother to call it a hash at that point? -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV "All of this is for nothing if we don't go to the stars" - JMS/B5 "If Java had true garbage collection, most programs would delete themselves upon execution." -- Robert Sewell
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