1619317 - Substantial increase in 32 bit users on 64 bit OS around the first week of Decemeber

Status: RESOLVED FIXED

(Core :: Widget: Win32, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

In the first week of December 2019 we seem to have had a bunch of users move from 32 bit Windows to 64 bit Windows.

You can see this in this chart of isWow64:
https://datastudio.google.com/s/lIAvPpsI2m0

It also showed up here:
https://firefoxgraphics.github.io/telemetry/#view=trends in the "Firefox CPU Architecture" section.

and here: https://data.firefox.com/dashboard/hardware in the "Operating Systems by Architecture" table.

We've also noticed an uptick in OOMs on 32 bit lately, like in bug 1617730 and an omtp bug which perhaps started around the same time.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

It looks like this switch only happened on Win7: https://datastudio.google.com/open/181GE2_2Y2J8YoN1z8sfJqCbflircwSN-

Comment 2

[Jeff Muizelaar [:jrmuizel]]

It seems like this could've been caused by Firefox 71 perhaps by bug 1553546.

Comment 3

[Emma Malysz]

Looking into it more now!

Comment 4

[Jeff Muizelaar [:jrmuizel]]

Yeah, I confirmed the big switch happened in Firefox 71

Comment 5

[Jeff Muizelaar [:jrmuizel]]

You can see it happen here: https://sql.telemetry.mozilla.org/queries/68815/source#173775

Comment 6

[:Gijs (he/him)]

(In reply to Jeff Muizelaar [:jrmuizel] from comment #2)

It seems like this could've been caused by Firefox 71 perhaps by bug 1553546.

Can you elaborate? That bug only touched measurements, not what people actually run, right? I don't see anything using the iswow64 data from the sysinfo service besides telemetry, so I wouldn't have expected this to e.g. affect updates (and even if it did, it wouldn't make sense for this to start with the release that first included these changes; the code would need to be there first, for it to start affecting updates...)

Comment 7

[Jeff Muizelaar [:jrmuizel]]

My current theory is that bug 1553546 or another change Firefox 71 introduced a measurement change and we're now reporting different values for IsWow64. It seems unlikely that an actual change in user's system would produce a graph like the above that aligns with the update to 71.

It's likely possible to check what proportion of users that switched from IsWow64=false to IsWow64=true when updating to 71 vs not but that requires a sql query that's beyond my skills.

Comment 8

[Emma Malysz]

Attachment: Bug 1619317, ensure we set isWow64 to the correct value after taking it off the main thread

Comment 9

[Emma Malysz]

I have a patch up right now that I believe will fix this issue (still testing). I think the problem is that I set info.isWow64 in the incorrect place

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/13d991470822
ensure we set isWow64 to the correct value after taking it off the main thread r=aklotz

Comment 11

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/13d991470822

Comment 12

[Jeff Muizelaar [:jrmuizel]]

Emma, can we uplift this to 75?

Comment 13

[Emma Malysz]

Comment on attachment 9130458 [details]
Bug 1619317, ensure we set isWow64 to the correct value after taking it off the main thread

Beta/Release Uplift Approval Request

• User impact if declined: We will be collecting incorrect telemetry numbers for our 32 bit users on 64 bit OS.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This implements a check that was missed in bug 1553546 when we moved this information off the main thread.
• String changes made/needed: None

Comment 14

[Julien Cristau [:jcristau]]

Comment on attachment 9130458 [details]
Bug 1619317, ensure we set isWow64 to the correct value after taking it off the main thread

approved for 75.0b2

Comment 15

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/releases/mozilla-beta/rev/0c70908982fd