Following the recent discussion about PGO, I really wanted to understand what benefits PGO gives Firefox on Windows, if any--I was skeptical. Rafael (IIRC) posted some Talos numbers, but I didn't know how to interpret them. So I decided to try a few simple experiments to try to falsify the hypothesis that "PGO has user-perceivable benefits".
Experimental setup: Windows builds from http://hg.mozilla.org/mozilla-central/rev/5f4a6a474455 on a Windows 7 Xeon. I took opt and pgo builds from the tbpl links. Experiment 1: cold startup time I used a camera to measure time from pressing enter on a a command line until the Fx window was completely shown. results: opt: 3.025 seconds pgo: 1.841 - A clear win for PGO. I'm told that there is a startup time optimization that orders omni.ja that only runs in PGO builds. So it's not necessarily from the PGO itself, but at least it means the current PGO builds really are better. Experiment 2: JS benchmarks I ran SunSpider and V8. I would have run Kraken too, but it takes longer to run and I already had significant results by then. I did 1-2 runs. Below I show the average, rounded off to not show noise digits. results: opt pgo SunSpider 250 200 (seconds) V8 8900 9400 ("score") - Another clear win for PGO. (Side note: I've recorded startup times for myself, with my normal profile, of ~30 seconds. I assumed that was just normal, so today I looked on Telemetry and saw that only 5-8% of startup times are that long. (I wish I knew what % of cold startups that is.) Today's results were with a clean profile, so it seems like my normal profile must be busting my startups (and others') badly. It would be really nice to make startup time independent of profile.) Dave _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
