By: Ilya Lipovsky (lipovsky.delete@this.cs.bu.edu), February 22, 2008 6:27 pm
Room: Moderated Discussions
Linus Torvalds (torvalds@osdl.org) on 2/15/08 wrote:
>David Patterson (pattrsn@cs.berkeley.edu) on 2/15/08 wrote:
>>* The goal is to raise the level of abstraction to allow
>>people the space that we'll need to be able to make the
>>manycore bet work, rather than to be hamstrung by 15-year
>>old legacy code written in 30-year old progamming
>Well, you basically start off by just assuming it can
>work, and that nothing else can.
>That's a big assumption. It's by no means something you
>should take for granted. It's a wish that hasn't come to
>fruition so far, and quite frankly, I don't think people
>are really any closer to a solution today than they were
>two decades ago.
>The fact that you can find application domains where it
>does work isn't new.
>We've had our CM-5's, we've had our Occam programs, and
>there's no question they worked. The question is whether
>they work for general-purpose computing, and that one is
>still unanswered, I think.
>>* Apparently some readers skipped the part where we looked
>>at the SPEC benchmarks, the embedded EEMBBC benchmarks,
>>and then interviewed experts in databases, machine
>>learning, graphics as well as high performance computing
>>in trying to see if there was a short list of design
>No, I don't think people missed that. But you simplified
>those questions down to the point where it's not clear that
>your answers matched the question any more.
>For example, sure, you can claim that gcc boils down to
>a "finite state machine". In a sense pretty much
>anything boils down to that (are we Turing compete
>or not?), but that doesn't really say that the dwarf would
>be at all representing what gcc really ends up doing.
>And one of the projects I work on is almost purely a
>"graph traversal with hashing", so it should match your
>dwarf to a T, but the thing is, the biggest issue is how
>to minimize the size of the graph you have to traverse, not
>to traverse it as fast as possible. The problem isn't CPU
>time, it's memory and IO footprint.
>And I don't think that is unheard of elsewhere. The core
>algorithm could well be parallelizable, but the problem
>isn't the linear CPU speed, it's the things outside
>the CPU.
>>Our bet is that the best applications, the best programming
>>languages, the best libraries,... have not yet been
>If we are looking at a 100+ core future, I certainly agree.
>>If we as field can succeed at this amazingly difficult
>>challenge, the future looks good. If not, then performance
>>increases we have relied upon for decades will come
>>to an abrupt halt, likely dimishing the future of the IT
>Here's my personal prediction, and hey, it's just that: a
>(a) we'll continue to be largely dominated by linear
>issues in a majority of loads.
>(b) this may well mean that the future of GP computing
>ends up being about small, and low power, and being
>absolutely everywhere (== really dirty cheap).
>IOW, the expectation of exponential performance scaling
>may simply not be the thing that we even want. Yeah,
>we'll get it for those nice parallel loads, but rather
>than expect everything to get there, maybe we should just
>look forward to improving IT in other directions than pure
>If the choice becomes one of "parallel but fast machines"
>and "really small and really cheap and really low power
>and 'fast enough' ones with just a coule of cores", maybe
>people will really pick the latter.
>Especially if it proves that the parallel problem really
>isn't practically solvable for a lot of things that people
>want to do.
>Pessimistic? It depends on what you look forward to.

I dug up an interesting UCLA paper on how to utilize multiple core to speed up linear workloads:


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TopicPosted ByDate
Multicore is unlikely to be the ideal answer.Anders Jensen2008/02/14 04:24 AM
  And the links..Anders Jensen2008/02/14 04:25 AM
    Disappointing..Linus Torvalds2008/02/14 10:17 AM
      Disappointing..Mark Roulo2008/02/14 11:03 AM
        LOL (NT)Linus Torvalds2008/02/14 05:43 PM
      Disappointing..David Patterson2008/02/15 11:53 AM
        Disappointing..Linus Torvalds2008/02/15 05:01 PM
          Disappointing..anon2008/02/15 08:54 PM
            Disappointing..JasonB2008/02/19 07:45 PM
          Disappointing..Ilya Lipovsky2008/02/22 06:27 PM
          Disappointing..Scott Bolt2008/03/16 11:36 AM
        Need for new programming languagesVincent Diepeveen2008/02/19 06:18 AM
          Need for new programming languagesPete Wilson2008/02/24 11:41 AM
        Disappointing..Zan2008/02/25 10:52 PM
      Disappointing..Robert Myers2008/02/19 09:47 PM
        Disappointing..Fred Bosick2008/02/22 06:38 PM
          Disappointing..Robert Myers2008/03/01 01:17 PM
        The limits of single CPU speed are here.John Nagle2008/03/14 10:55 AM
          The limits of single CPU speed are here.Howard Chu2008/03/15 01:02 AM
            The limits of single CPU speed are here.slacker2008/03/15 08:08 AM
              The limits of single CPU speed are here.Howard Chu2008/03/17 01:47 AM
                The limits of single CPU speed are here.slacker2008/03/17 10:04 AM
    And the links..Howard Chu2008/02/14 12:58 PM
      I take some of that backHoward Chu2008/02/14 01:55 PM
      And the links..Jesper Frimann2008/02/14 02:02 PM
      And the links..Ilya Lipovsky2008/02/15 02:24 PM
        And the links..iz2008/02/17 10:55 AM
          And the links..JasonB2008/02/17 07:09 PM
            And the links..Ilya Lipovsky2008/02/18 01:54 PM
              And the links..JasonB2008/02/18 10:34 PM
                And the links..Thiago Kurovski2008/02/19 07:01 PM
                  And the links..iz2008/02/20 10:36 AM
                And the links..Ilya Lipovsky2008/02/20 03:37 PM
                  And the links..JasonB2008/02/20 06:28 PM
        And the links..JasonB2008/02/17 06:47 PM
          And the links..Ilya Lipovsky2008/02/18 02:27 PM
            And the links..JasonB2008/02/18 10:00 PM
              And the links..JasonB2008/02/19 03:14 AM
              And the links..Ilya Lipovsky2008/02/20 04:29 PM
                And the links..JasonB2008/02/20 06:14 PM
                  And the links..Ilya Lipovsky2008/02/21 11:07 AM
    And the links..Howard Chu2008/02/14 01:16 PM
      And the links..Jukka Larja2008/02/15 03:00 AM
      Berkeley View on ParallelismDavid Kanter2008/02/15 11:41 AM
        Berkeley View on ParallelismHoward Chu2008/02/15 12:49 PM
          Berkeley View on ParallelismDavid Kanter2008/02/15 03:48 PM
            Berkeley View on ParallelismHoward Chu2008/02/17 05:42 PM
              Berkeley View on Parallelismnick2008/02/17 09:15 PM
                Berkeley View on ParallelismHoward Chu2008/02/18 04:23 PM
                  Berkeley View on Parallelismnick2008/02/18 10:03 PM
                    Berkeley View on ParallelismHoward Chu2008/02/19 01:39 AM
                  Berkeley View on Parallelismrcf2008/02/19 12:44 PM
                    Berkeley View on ParallelismHoward Chu2008/02/19 03:25 PM
              Average programmersanon2008/02/18 12:40 PM
        Berkeley View on ParallelismJasonB2008/02/15 08:02 PM
        Berkeley View on ParallelismJasonB2008/02/15 08:02 PM
          Berkeley View on ParallelismDean Kent2008/02/15 08:07 PM
          Berkeley View on ParallelismRay2008/02/20 03:20 PM
            Berkeley View on ParallelismJasonB2008/02/20 06:11 PM
              Berkeley View on ParallelismFritzR2008/02/24 03:08 PM
          rubyinline, etc.nordsieck2008/02/22 03:38 PM
            rubyinline, etc.JasonB2008/02/23 05:53 AM
              rubyinline, etc.nordsieck2008/03/02 01:40 AM
                rubyinline, etc.Michael S2008/03/02 02:49 AM
                  rubyinline, etc.Dean Kent2008/03/02 07:41 AM
                    rubyinline, etc.Michael S2008/03/02 08:19 AM
                      rubyinline, etc.Dean Kent2008/03/02 08:30 AM
                        rubyinline, etc.JasonB2008/03/02 05:26 PM
                rubyinline, etc.JasonB2008/03/02 06:01 PM
                  rubyinline, etc.Anonymous2008/03/03 02:11 AM
                    rubyinline, etc.JasonB2008/03/03 09:40 AM
                      rubyinline, etc.Foo_2008/03/09 09:59 AM
                        rubyinline, etc.JasonB2008/03/10 01:12 AM
                        rubyinline, etc.Gabriele Svelto2008/03/10 02:22 AM
                          rubyinline, etc.JasonB2008/03/10 04:35 AM
                            C++ for beginnersMichael S2008/03/10 05:16 AM
                              C++ for beginnersJasonB2008/03/10 06:35 AM
                          C++Michael S2008/03/10 04:55 AM
                rubyinline, etc.Linus Torvalds2008/03/03 11:35 AM
                  rubyinline, etc.Dean Kent2008/03/03 02:35 PM
                    rubyinline, etc.JasonB2008/03/03 03:57 PM
                      rubyinline, etc.Dean Kent2008/03/03 08:10 PM
                        rubyinline, etc.Michael S2008/03/04 01:53 AM
                          rubyinline, etc.Dean Kent2008/03/04 07:51 AM
                            rubyinline, etc.Michael S2008/03/04 08:29 AM
                              rubyinline, etc.Dean Kent2008/03/04 08:53 AM
                                rubyinline, etc.Michael S2008/03/04 11:20 AM
                                  rubyinline, etc.Dean Kent2008/03/04 02:13 PM
                                    read it. thanks (NT)Michael S2008/03/04 04:31 PM
                  efficient HLL'sPatrik Hägglund2008/03/04 03:34 PM
                    efficient HLL'sWes Felter2008/03/04 09:33 PM
                      efficient HLL'sPatrik Hägglund2008/03/05 01:23 AM
                        efficient HLL'sMichael S2008/03/05 02:45 AM
                          efficient HLL'sWilco2008/03/05 05:34 PM
                            efficient HLL'sHoward Chu2008/03/05 07:11 PM
                              efficient HLL'sWilco2008/03/06 02:27 PM
                    efficient HLL'sanon2008/03/05 08:20 AM
      And the links..Groo2008/02/17 04:28 PM
        And the links..Vincent Diepeveen2008/02/18 02:33 AM
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