Date: Thu, 6 Mar 1997 00:24:04 +1100 (EDT) From: Darren Reed <avalon@coombs.anu.edu.au> To: mingo@pc5829.hil.siemens.at (Ingo Molnar) Cc: davem@jenolan.rutgers.edu, wong@rogerswave.ca, alan@cymru.net, imb@scgt.oz.au, dg@root.com, netdev@roxanne.nuclecu.unam.mx, hackers@freebsd.org Subject: Re: ok, final sockhash changes, new diff Message-ID: <199703051327.FAA17044@freefall.freebsd.org> In-Reply-To: <Pine.LNX.3.95.970304160729.1660B-100000@pc5829.hil.siemens.at> from "Ingo Molnar" at Mar 4, 97 04:17:07 pm
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In some mail from Ingo Molnar, sie said: > > > On Tue, 4 Mar 1997, David S. Miller wrote: > > > actually, this paper by Larson talks about the hash table with n > > items in each packet. when the packet axceed n items, it double its > > table size. [...] > > > For servers with bursty patterns (ie. nearly all heavily loaded > > machines) this scheme can be extremely inefficient, you get this yo-yo > > effect in the chain lengths over ~4 second intervals of time at 12,000 > > Web operations per second, but then again once you reach that point > > TIME_WAIT begins to kill you as well and many commercial UNIX's break > > rfc1122 just to work around this, and that causes so many problems > > that I don't want to talk about it. > > people with big servers should simply choose bigger HASH_TABLE_SIZE. As > the caches most probably get trashed between two packet receives anyways, > this seems to be a non-issue. [3k more nonswappable memory for size 1024, > who cares?] > > as a rule of thumb: SIZE := max(256,"wc -l /proc/net/tcp") ? > > [the hash table should be kept compressed to avoid cache pollution] Why can't it "autoconfigure" according to the size of your RAM ? i.e. more RAM => bigger server => more users/network connections Darren p.s. of course it should be possible to manually override this "number', for extreme cases, but why build kernels dumb ?help
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