On Thu, Nov 24, 2016 at 3:07 AM, serge guelton <sguel...@quarkslab.com> wrote:
> On Mon, Nov 21, 2016 at 03:26:19PM -0800, Kevin Modzelewski wrote: > > 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. > > That raised a second question: do you collect branch / hotness info > during lower tier jitted code run, so as to improve performance of > higher tiers ? > We don't (yet) do code placement optimizations. We should be getting some basic amount of this, though, by our generated code being grouped by "tier that compiled it" which is highly correlated with hotness. > > > 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. > > ok. Are you just « putting hot stuff in the hot section » or did you try > to specify an ordering to further improve locality? (I don't know if it's > possible, it's mentionned in one of the paper) > We pull the function order from the PGO build and ask the non-pgo build to use the same order, so it's up to whatever the C compiler did. Though to keep things tractable we only do this for functions that have some non-negligible hotness. I think this does help with overall performance of the non-pgo build, but our main goal was performance consistency. > > Thanks, > > Serge >
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