Messages in this thread | | | Subject | Re: bisected: futex regression >= 3.14 - was - Slowdown due to threads bouncing between HT cores | From | Mike Galbraith <> | Date | Wed, 08 Oct 2014 19:52:20 +0200 |
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On Wed, 2014-10-08 at 18:45 +0200, Steinar H. Gunderson wrote: > On Wed, Oct 08, 2014 at 06:14:18PM +0200, Thomas Gleixner wrote: > > It looks far more like an issue with the stocking fish code, but hell > > with futexes one can never be sure. > > OK, maybe we should move to a more recent Stockfish version first of all; > the specific benchmark was about that specific binary, but for tracking down > futex issues we can see if more recent code fixes it (the SMP in this thing > keeps getting developed).
Mine was self build master, downloaded as a tarball.
> I'm moving to 2ac206e847a04a7de07690dd575c6949e5625115 (current head) of > https://github.com/mcostalba/Stockfish.git, and building with > “make -j ARCH=x86-64-bmi2”. > > I still don't see any hangs, but I do see the same behavior of moving around > between CPUs as the older version exhibited. In a test run (using the given > test script, just with 28 replaced by 20), I get 18273 kN/sec with default, > and 21875 kN/sec when using taskset.
Sure, that will likely be workqueues or whatnot running when one of the chess threads wakes, so select_idle_sibling() shows one of its two faces.. the butt ugly one. That's what I wanted to play with on a too darn big socket box when I discovered the thing didn't want to play.
-Mike
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