1964113 - Remove unused LUL code from the base profiler

Status: RESOLVED FIXED

(Core :: Gecko Profiler, task)

Description

[Markus Stange [:mstange]]

The base profiler, which is used when profiling the very start of Firefox startup, i.e. before libxul has finished loading, ships its own copy of LUL on Linux + Android. However, this copy is currently not used!

In fact, we don't even do frame-pointer based stack walking in the base profiler on Linux. Native stackwalking support was disabled entirely for the base profiler on Linux in bug 1658232 in this patch:
https://phabricator.services.mozilla.com/D86506

I think we should just remove the unused code. And independently we can make the base profiler use frame pointers to unwind native stacks.

But it seems that people don't need a working base profiler on Linux anyway, or someone would have complained about missing stacks before. The base profiler was primarily added for Windows, where Firefox would sometimes run injected code from third parties before it started loading xul.dll.

Comment 1

[Nazım Can Altınova [:canova][:canaltinova on phabricator]]

Attachment: Bug 1964113 - Remove LUL from the baseprofiler r?mstange

Comment 2

[Markus Stange [:mstange]]

Good news, it looks like the unused code didn't actually make it into the binary.
Size profile of Linux x64 firefox-bin: https://share.firefox.dev/4jG0BUh

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c792971da78e
Remove LUL from the baseprofiler r=mstange,profiler-reviewers

Comment 4

[agoloman]

https://hg.mozilla.org/mozilla-central/rev/c792971da78e