Re: DP performance

[Danial Thom <danial_thom@xxxxxxxxx>]

--- Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
wrote:
> :No, sorry. I thought thats what you guys were
> :doing. How long do you think it will be before
> :any of the 4.x derivatives are actually better
> :than 4.x?
> :
> :Danial
> 
>     Well, the main issue is that the original
> BSD code (and the
>     original linux code for that matter) was
> not designed to operate
>     in an MP environment.  Fixing it requires
> rewriting most of the
>     major subsystems in the kernel.
> 
>     We are fairly close to being able to
> parallelize the protocol
>     stacks.  We can certainly run the interrupt
> *threads* on any
>     cpu, once we get the BGL turned off in the
> threads.  Directing
>     an actual hard interrupt to the appropriate
> cpu is harder.

Is there any evidence that chopping up the kernel
into threads yields a net gain with 2 processors?
Linux is supposedly very good at MP, and linux
with 2 processors is still outperformed by
FreeBSD 4 with one. How many processors do you
need to make up for the inefficiencies you create
by threading the kernel? Or do we just assume
that more is better? Probably running 2 distinct
kernels on a single machine would yield better
results than a single, threaded kernel. It seems
like a lot of work to just get to where you were
before.

Danial

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