Post looking at BTB behavior and size

By: Travis Downs (travis.downs.delete@this.gmail.com), May 10, 2021 2:57 pm
Room: Moderated Discussions
A worthwhile read on probing BTB behavior and size, including Intel, AMD and M1 chips:

How many ifs are too many?

One thing that caught my eye is that Marek measures better than one taken branch per cycle on Zen 3 (EPYC 7713), at least for code that fits in the L1 icache. That surprises me since I'm not aware of any mainstream uarch that can execute more than 1 taken branch per cycle (plenty can execute more than 1 untaken branches per cycle).

Maybe it's just measurement error (e.g., due to turbo above the expected frequency), or can Zen 3 really do this?
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TopicPosted ByDate
Post looking at BTB behavior and sizeTravis Downs2021/05/10 02:57 PM
  Post looking at BTB behavior and sizeAnon2021/05/10 04:43 PM
    Post looking at BTB behavior and sizeTravis Downs2021/05/10 08:59 PM
    Post looking at BTB behavior and sizeLinus Torvalds2021/05/11 10:13 AM
  RKL taken branch throughputChester2021/05/10 05:25 PM
    RKL taken branch throughputTravis Downs2021/05/10 09:00 PM
      RKL taken branch throughputChester2021/05/11 10:04 PM
        RKL taken branch throughputTravis Downs2021/05/14 10:34 PM
          RKL taken branch throughput---2021/05/15 10:07 AM
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