1061772 - Profiler cost percentage should be calculated based on number of samples and not samples delta time

Status: RESOLVED FIXED

(DevTools :: Performance Tools (Profiler/Timeline), defect, P2)

Description

[Benoit Girard (:BenWa)]

Attachment: Screenshot

See bug 1061759, I'm going to be calling the 3rd column 'Samples' from here on out.

If you look at the screenshot, compare the (root) node with DSC_allocId. Notice that (root) has 100% cost but DSC_allocId has 17%. This doesn't seem to add up at all with the call/samples count.

Profile from bug 1045715.

Comment 1

[Victor Porof [:vporof][:vp]]

The 17% is time, not samples.

Comment 2

[Benoit Girard (:BenWa)]

What is the 3rd column and why is the 3rd column not equal to the second column multiplied by a constant?

Comment 3

[Benoit Girard (:BenWa)]

I discussed with victor in person. We added a sample time back in the day to the profiler backend to know when the profiler failed to capture a sample on time. In the screenshot we're using this to compute duration/time but we agreed that this wasn't accurate to report as Cost/Time since really we don't know what occurred during these missed samples and charging that to the site where we finally take the sample is misleading.

Comment 4

[Victor Porof [:vporof][:vp]]

Attachment: v1

Comment 5

[Patrick Brosset <:pbro>]

Comment on attachment 8491677 [details] [diff] [review]
v1

Review of attachment 8491677 [details] [diff] [review]:
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Alright, this change makes sense to me. In these kinds of UIs though, it's hard to know what each column mean and how it's calculated, so it's hard for a user to know what to look for when investigating problems. So I think column header tooltips would help here.

Comment 6

[Victor Porof [:vporof][:vp]]

https://hg.mozilla.org/integration/fx-team/rev/30a7753deb4b

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/30a7753deb4b