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
> [EMAIL PROTECTED]
>
>
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