1636561 - about:processes shows excessive CPU usage from idle Firefox under Windows

Status: RESOLVED DUPLICATE of bug 1637559

(Core :: DOM: Content Processes, defect, P3)

Description

[Chris Peterson [:cpeterson]]

Attachment: screenshot.png

Windows Task Manager says my firefox.exe processes are pretty idle, but about:processes sometimes says "browser" uses up to 500% User and 1500% Kernel. See the attached screenshot of Fx78 Nightly with only the about:processes tab open and about:processes is reporting the "browser" process is using 79% CPU (User) and 278% CPU (Kernel).

I think Windows' CPU usage APIs can report CPU usage over 100% for machines that have multiple cores. Regardless, I would not expect my idle Firefox to be using so much CPU.

Ironically, about:processes consumes a lot of CPU, spiking my parent process to ~60% CPU (in Windows Task Manager) every second or so.

Yoric says: "On macOS, I get good results but I have reports of inconsistent results on Linux, too. It's possible that the underlying API was only tested on macOS."

Comment 1

[Chris Peterson [:cpeterson]]

Tracking for Fission M6b because we want about:processes to report accurate numbers soon, before we have many Nightly users using it.

Comment 2

[David Teller [:Yoric] - still alive but not very active]

FWIW, the Linux bug is being handled in bug 1636203. It was an unnoticed typo or merge error in the Linux implementation of the underlying API. I'll check if the same shows up in the Windows version.

Comment 3

[David Teller [:Yoric] - still alive but not very active]

No typo/merge error that I can find and the arithmetics of the Windows version looks good.
I don't have a Windows machine for building and testing at home, so it's a tad complicated for me to fix.

@tarek, do you have any idea?

Comment 4

[David Teller [:Yoric] - still alive but not very active]

Bug 1637559 fixes a clock problem which could be the root cause.

Comment 5

[Ryan VanderMeulen [:RyanVM]]

FWIW, I still see about:processes running my CPU at 25-30% whenever I open it.

Comment 6

[David Teller [:Yoric] - still alive but not very active]

(In reply to Ryan VanderMeulen [:RyanVM] from comment #5)

FWIW, I still see about:processes running my CPU at 25-30% whenever I open it.

Where do you see that? OS Task Manager or about:processs?

Comment 7

[Ryan VanderMeulen [:RyanVM]]

Both show it

Comment 8

[David Teller [:Yoric] - still alive but not very active]

Ok, so it's a different bug. about:processes really uses too much CPU.
Filed your problem as bug 1652000.

Comment 10

[Chris Peterson [:cpeterson]]

Clearing Fission Milestone for bugs resolved as duplicates. We don't need to track duplicates.