Messages in this thread | | | Date | Fri, 1 Jul 2022 06:50:28 -0700 | From | "Paul E. McKenney" <> | Subject | Re: plumbers session on profiling? |
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On Fri, Jul 01, 2022 at 01:49:06PM +0200, Peter Zijlstra wrote: > On Fri, Jul 01, 2022 at 03:17:54AM -0700, Bill Wendling wrote: > > On Fri, Jul 1, 2022 at 2:02 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > On Tue, Jun 28, 2022 at 07:08:48PM +0200, Jose E. Marchesi wrote: > > > > > > > > [Added linux-toolchains@vger in CC] > > > > > > > > It would be interesting to have some discussion in the Toolchains track > > > > on building the kernel with PGO/FDO. I have seen a raise on interest on > > > > the topic in several companies, but it would make very little sense if > > > > no kernel hacker is interested in participating... anybody? > > > > > > I know there's been a lot of work in this area, but none of it seems to > > > have trickled down to be easy enough for me to use it. > > > > We use an instrumented kernel to collect the data we need. It gives us > > the best payoff, because the profiling data is more fine-grained and > > accurate. (PGO does much more than make inlining decisions.) > > > > If I recall correctly, you previously suggested using sampling data. > > (Correct?) Is there a document or article that outlines that process? > > IIRC Google has LBR sample driven PGO somewhere as well. ISTR that being > the whole motivation for that gruesome Zen3 BRS hack. > > Google got me this: https://research.google.com/pubs/archive/45290.pdf
Whatever else, please refrain from using PGO and friends to drive data-value speculation!
Thanx, Paul
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