Re: Automatic parallelization - was Re: LISP Object Oriented?

On Jan 30, 5:59 pm, Paul Wallich <p...@xxxxxxxxx> wrote:


The big question is whether inefficient use of cores is a bad thing.

It's a bad thing because it's making poor use of expensive silicon.
The only valid (as opposed to marketing) reason to out more cores on a
chip is that it is (or is hoped to be) the best way of getting more
performance out of the resources (silicon in other words) available.
If the cores are starving for memory then a better use of the
resources would be to deal with that problem.

(This is similar to the reason why processors typically don't
speculatively execute both sides of a branch: the maximum possible
utilization of that is 50%, so it's generally better to predict and
then speculatively execute the branch you predict to be taken, which
can do much better than 50% on typical code.)

--tim

.

Relevant Pages

  • Re: To Context switch or Spin
    ... core, two virtual cores. ... FSB, steals CPU execution resources, and dirties critical OS ... Then when someone upgrades their ...
    (comp.programming.threads)
  • Re: [9fans] Plan 9 and multicores/parallelism/concurrency?
    ... 100s of cores per die. ... much any sophisticated scheduling. ... not sure thread placement belongs in the kernel. ... that lets me deal with affinitizing 3 resources that run at different ...
    (comp.os.plan9)
  • Re: [RFC PATCH 01/17] shm-signal: shared-memory signals
    ... returns and allows the vcpu to re-enter guest mode immediately. ... we need to actually use those cores IMO. ... There will be a point in the curve where the cost of cache ... bring some of the features of advanced silicon to commodity resources. ...
    (Linux-Kernel)
  • Re: Detecting CPUs and cores
    ... doesn't arise from the die layouts per se, ... The cores may share resources ... of them is far more involved than simply counting cores or chips. ... As a Java programmer, one is divorced from the details of the "actual" differences that you describe. ...
    (comp.lang.java.programmer)