Date: Wed, 25 Jul 2001 13:05:05 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Zhihui Zhang <zzhang@cs.binghamton.edu> Cc: Terry Lambert <tlambert2@mindspring.com>, vishwanath pargaonkar <vishubp@yahoo.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: cluster size Message-ID: <Pine.BSF.4.21.0107251301540.4973-100000@InterJet.elischer.org> In-Reply-To: <Pine.SOL.4.21.0107251350010.20991-100000@opal>
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Basically you want it to hold a number of mbufs and you want it to fit into a page nicely. you probably want it to have a bit of extra rume for oversized packets too. 2K seems a good fit. nothing magic about it however. (should be less than a page, bigget than an ehternet packet(plus a bit) 4096/3 is 1365.... too small 4096/2=2048 ok.. 4096/1 too wasteful. On Wed, 25 Jul 2001, Zhihui Zhang wrote: > > > On Tue, 24 Jul 2001, Terry Lambert wrote: > > > Zhihui Zhang wrote: > > > > Hi, > > > > in freebsd can we change the cluster size from 2048 > > > > bytes.If yes how can we do that? > > > > do we have to configure in some file? > > > > > > You must be asking why the mbuf cluster size is chosen as 2048, right? It > > > is probably a tradeoff between memory efficient and speed. > > > > Ask yourselves: > > > > "What is the minimum cluster size I would have to have > > to be able to contain the maximum MTU worth of data, > > yet remain an even multiple of sizeof(mbuf) -- 256 > > bytes?" > > A dumb question: why even not odd multiple? > > -Zhihui > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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