Date: Wed, 25 Jul 2001 14:17:38 -0400 (EDT) From: Zhihui Zhang <zzhang@cs.binghamton.edu> To: Bosko Milekic <bmilekic@technokratis.com> Cc: Terry Lambert <tlambert2@mindspring.com>, vishwanath pargaonkar <vishubp@yahoo.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: cluster size Message-ID: <Pine.SOL.4.21.0107251416550.21505-100000@opal> In-Reply-To: <20010725140737.A25132@technokratis.com>
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I see. It has something to do with the power-of-two allocator we are using inside the kernel. -Zhihui On Wed, 25 Jul 2001, Bosko Milekic wrote: > > On Wed, Jul 25, 2001 at 01:51:51PM -0400, 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 > > It actually has to do with the fact that 2K is the only size equal to > or greater than the maximum MTU worth of data that can be multiplied to a page > size without any leftover (in other words, page size modulo 2K is zero). > > -- > Bosko Milekic > bmilekic@technokratis.com > > > 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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