146378 2015-06-26 21:27:59 -0700 [JetStream] Raise the percentile of mandreel-latency and splay-latency 2015-06-27 20:48:11 -0700 1 1 1 Unclassified WebKit Tools / Tests 528+ (Nightly build) All All RESOLVED FIXED P2 Normal --- 1 fpizlo fpizlo barraclough basile_clement benjamin commit-queue ggaren mark.lam mhahnenb mmirman msaboff nrotem oliver rniwa saam sam oldest_to_newest 1105143 0 fpizlo 2015-06-26 21:27:59 -0700 The current percentile is 95%. When I looked at the sample lists in our GC, it was clear that the worst 5% samples completely amortize our GC pauses. Our GC pauses can be quite bad. Clearly, splay-latency is meant to test whether we have an incremental GC that ensures that you don't have bad worst-case pauses. But 95% is too small, because it doesn't really capture those pauses. Raising the percentile to above 99% appears to do the trick. 99.5% or more seems like a good bet. The trade-off there is just that if we set it too high, then we won't have enough statistics. Doing this very clearly rewards GCs that are incremental, and punishes GCs that aren't (like ours). That's what we want, since in the future we want to use this test to guide any improvements to the worst-case performance of our GC. The way that the percentile is selected will also affect mandreel-latency. That's a good thing, because 95% is probably too low for that test as well. That test ends up with >10k samples. The goal of using 95% in the first place was to get enough samples to have a stable average. But if we have >10k samples, we can push that percentile up much higher and still get good statistics while achieving the effect we want - i.e. getting the worst case. I don't think that we need to do the same thing for cdjs. That test only takes 200 samples, so 95% means we report the average of the worst 10 samples. That's probably good enough. 1105144 1 255691 fpizlo 2015-06-26 21:30:34 -0700 Created attachment 255691 the patch 1105147 2 255691 mark.lam 2015-06-26 22:25:34 -0700 Comment on attachment 255691 the patch rs=me 1105244 3 fpizlo 2015-06-27 20:48:11 -0700 Landed in http://trac.webkit.org/changeset/186041 255691 2015-06-26 21:30:34 -0700 2015-06-26 22:25:34 -0700 the patch blah.patch text/plain 4539 fpizlo SW5kZXg6IFBlcmZvcm1hbmNlVGVzdHMvQ2hhbmdlTG9nCj09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0KLS0tIFBlcmZvcm1h bmNlVGVzdHMvQ2hhbmdlTG9nCShyZXZpc2lvbiAxODYwMjEpCisrKyBQZXJmb3JtYW5jZVRlc3Rz L0NoYW5nZUxvZwkod29ya2luZyBjb3B5KQpAQCAtMSwzICsxLDM3IEBACisyMDE1LTA2LTI2ICBG aWxpcCBQaXpsbyAgPGZwaXpsb0BhcHBsZS5jb20+CisKKyAgICAgICAgW0pldFN0cmVhbV0gUmFp c2UgdGhlIHBlcmNlbnRpbGUgb2YgbWFuZHJlZWwtbGF0ZW5jeSBhbmQgc3BsYXktbGF0ZW5jeQor ICAgICAgICBodHRwczovL2J1Z3Mud2Via2l0Lm9yZy9zaG93X2J1Zy5jZ2k/aWQ9MTQ2Mzc4CisK 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