Threadripper 32 core review

By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), August 13, 2018 2:12 pm
Room: Moderated Discussions
wumpus (lost.delete@this.in.a.cave) on August 13, 2018 9:32 am wrote:
> Per Hesselgren (perhesselgren.delete@this.yahoo.se) on August 13, 2018 8:50 am wrote:
> > Threadripper on Anandtech
>
> Looks like coherency isn't an issue for 32 cores, but obviously not everything scales perfectly.

Even loads that should scale really well (like the chromium build) seem to have hit the point of negative scaling here, with a 32c/64t 2990WX doing worse than a 16c/32t 2950X.

I do suspect it's mostly the load that doesn't scale any more at that point, with the negative scaling coming from more memory contention and perhaps half of the cores being further away from the memory controller.

Somebody who knows the Chromium build better might be able to tell how far they'd expect the build to scale, but even for simple things like a parallel build, you often hit serialization points (eg linking phases after you've built all your library files). And writing Makefiles that expose all the parallelism isn't trivial either.

But some of that may be "nobody spent any effort to scale past X cores because they are so rare, and build farms have their own scaling issues where IO may be the bottleneck".

So some of the scalability issues may just be "people haven't even tried to get that much parallelism". Others may be more fundamental.

Linus
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TopicPosted ByDate
Threadripper 32 core reviewPer Hesselgren2018/08/13 08:50 AM
  Threadripper 32 core reviewwumpus2018/08/13 09:32 AM
    Threadripper 32 core reviewLinus Torvalds2018/08/13 02:12 PM
      Threadripper 32 core reviewpgerassi2018/08/13 03:16 PM
        Threadripper 32 core reviewLinus Torvalds2018/08/13 03:48 PM
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          Threadripper 32 core reviewjuanrga2018/08/14 04:44 AM
            Threadripper 32 core reviewLinus Torvalds2018/08/14 09:37 AM
              Threadripper 32 core reviewjuanrga2018/08/14 11:18 AM
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