1636204 - about:processes shows unrealistic memory usage numbers on Linux.

Status: RESOLVED FIXED

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

Description

[Emilio Cobos Álvarez (:emilio)]

Attachment: Screenshot from 2020-05-07 19-01-25.png

See screenshot.

Comment 1

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

So, let's list what's wong:

• pid 0, that's basically impossible;
• missing processes;
• numbers are off.

I suspect that this and bug 1636203 are the same and that both are due to a bug in parsing /proc/[pid]/stat. It lives here, in case anybody wants to look at it.

Comment 2

[Ian Moody [:Kwan] (UTC+1)]

Attachment: Bug 1636204 - Use correct indexes for parsing /proc/[pid]/stat.

All the indexes were off by two, so the values were for completely different
measurements, and thus nonsense. Resident Set Size still doesn't seem to be
handled correctly, perhaps because it's being treated as a bytes count rather
than the page count it is somewhere, but with this change the Virtual Memory
figures match what system monitor displays.

Comment 3

[Ian Moody [:Kwan] (UTC+1)]

Attachment: about-processes.png

This is what I see after the two patches.

Comment 4

[Ian Moody [:Kwan] (UTC+1)]

Attachment: Bug 1636204 - Return size in bytes instead of page count for RSS in ProcInfo.

As noted in the comment /proc/[pid]/stat is returning the number of pages, but
this value is being used elsewhere as a bytes figure, so we need to multiply by
the page size to get that.

Comment 5

[Ian Moody [:Kwan] (UTC+1)]

Attachment: about-processes2.png

And with the third patch now resident memory matches.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c7713eb6813c
Use correct indexes for parsing /proc/[pid]/stat. r=Yoric
https://hg.mozilla.org/integration/autoland/rev/25f2f567dad6
Return size in bytes instead of page count for RSS in ProcInfo. r=Yoric

Comment 7

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/c7713eb6813c
https://hg.mozilla.org/mozilla-central/rev/25f2f567dad6