Oh sorry I was unclear, yes this is for the pyston binary itself, and yes PGO does a better job and I definitely think it should be used.
Separately, we often use non-pgo builds for quick checks, so we also have the system I described that makes our non-pgo build more reliable by using the function ordering from the pgo build.
On Mon, Nov 21, 2016 at 11:39 AM, serge guelton < serge.guelton@telecom-bretagne.eu> wrote:
On Sat, Nov 19, 2016 at 05:58:19PM -0800, Kevin Modzelewski wrote:
I think it's safe to not reinvent the wheel here. Some searching gives: http://perso.ensta-paristech.fr/~bmonsuez/Cours/B6-4/ Articles/papers15.pdf http://www.cs.utexas.edu/users/mckinley/papers/dcm-vee-2006.pdf https://github.com/facebook/hhvm/tree/master/hphp/tools/hfsort
Thanks Kevin for the pointers! I'm new to this area of optimization... another source of fun and weirdness :-$
Pyston takes a different approach where we pull the list of hot functions from the PGO build, ie defer all the hard work to the C compiler.
You're talking about the build of Pyston itself, not the jit generated code, right? In that case, how is it different to a regular
-fprofile-generate followed by several runs then -fprofile-use?PGO builds should perform better than marking some functions as hot, as it also includes info for better branch prediction too, right?