Re: Scaling noise

From: Anton Blanchard (anton_at_samba.org)
Date: 09/03/03

  • Next message: Michael Frank: "Re: [linux-usb-devel] 2.6.0-test4 - PL2303 OOPS - see also 2.4.22: OOPS on disconnect PL2303 adapter" 
    Date:	Wed, 3 Sep 2003 16:28:17 +1000
To: Larry McVoy <lm@work.bitmover.com>, Larry McVoy <lm@bitmover.com>, linux-kernel@vger.kernel.org

    > > > I've frequently tried to make the point that all the scaling for
    > > > lots of processors is nonsense. Mr Dell says it better:
    > > >
    > > > "Eight-way (servers) are less than 1 percent of the market and
    > > > shrinking pretty dramatically," Dell said. "If our competitors
    > > > want to claim they're No. 1 in eight-ways, that's fine. We
    > > > want to lead the market with two-way and four-way (processor
    > > > machines)."
    > > >
    > > > Tell me again that it is a good idea to screw up uniprocessor
    > > > performance for 64 way machines. Great idea, that. Go Dinosaurs!
    > >
    > > And does your 4 way have hyperthreading?
    >
    > What part of "shrinking pretty dramatically" did you not understand?
    > Maybe you know more than Mike Dell. Could you share that insight?

    Ok. But only because you asked nicely.

    Mike Dell wants to sell 2 and 4 processor boxes and Intel wants to sell
    processors with hyperthreading on them. Scaling to 4 or 8 threads is just
    like scaling to 4 or 8 processors, only worse.

    However, lets not end up in a yet another 64 way scalability argument here.

    The thing we should be worrying about is the UP -> 2 way SMP scalability
    issue. If every chip in the future has hyperthreading then all of sudden
    everyone is running an SMP kernel. And what hurts us?

    atomic ops
    memory barriers

    Ive always worried about those atomic ops that only appear in an SMP
    kernel, but Rusty recently reminded me its the same story for most of the
    memory barriers.

    Things like RCU can do a lot for this UP -> 2 way SMP issue. The fact it
    also helps the big end of town is just a bonus.

    Anton
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  • Next message: Michael Frank: "Re: [linux-usb-devel] 2.6.0-test4 - PL2303 OOPS - see also 2.4.22: OOPS on disconnect PL2303 adapter"