1753310 - Process CPU times shown in about:processes are dramatically underestimated on M1 Macs

Status: RESOLVED FIXED

(Toolkit :: Performance Monitoring, defect)

Description

[Florian Quèze [:florian]]

The % of CPU use of processes is almost always < 1% on my M1 Macbook, despite some threads of the process using more than 10% of a core.

Thankfully others have already figured this out. The pti.pti_total_user and pti.pti_total_system values returned by the proc_pidinfo / PROC_PIDTASKINFO are expressed in system ticks, rather than in nanoseconds. The mach_timebase_info function needs to be called to convert to nanoseconds.

On Macs with Intel CPUs, mach_timebase_info returns 1. On M1 CPUs, the result is 125/3.

Comment 1

[Florian Quèze [:florian]]

Attachment: Bug 1753310 - Fix process CPU times reported by about:processes, r=gerald.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/61491ef8a39c
Fix process CPU times reported by about:processes, r=gerald.

Comment 3

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/61491ef8a39c