1776694 - For local builds on desktop, we don't get symbols for libraries which are only loaded in child processes (plugin-container, libmozavcodec.so)

Status: RESOLVED FIXED

(Core :: Gecko Profiler, defect, P2)

Description

[Markus Stange [:mstange]]

Example profiles: https://share.firefox.dev/3HYUtnV , https://share.firefox.dev/3ynoWc5

Steps to reproduce:

1. Build Firefox locally.
2. Run the build and capture a profile.
3. Check the content process and the RDD process.

Expected results:
Every library that was compiled as part of the local build should have symbols.

Actual results:
On macOS, in the child process, there's an unsymbolicated frame near the root of the call tree in plugin-container.
On Linux, in the RDD process, the frames for libmozavcodec.so are unsymbolicated.

More generally, any library which is not loaded in the parent process doesn't have symbols.

Comment 1

[Markus Stange [:mstange]]

This is because we use Services.profiler.sharedLibraries to determine which absolute paths symbolication is allowed to access. It only returns libraries that are loaded in the parent process.

https://searchfox.org/mozilla-central/rev/bf6f194694c9d1ae92847f3d4e4c15c2486f3200/devtools/client/performance-new/popup/background.jsm.js#318-336

const profileCaptureResult = await Services.profiler
  .getProfileDataAsGzippedArrayBuffer()
  .then(
    profile => ({ type: "SUCCESS", profile }),
    error => {
      console.error(error);
      return { type: "ERROR", error };
    }
  );

const profilerViewMode = getProfilerViewModeForCurrentPreset(pageContext);
const sharedLibraries = Services.profiler.sharedLibraries;
const objdirs = getObjdirPrefValue();

const { createLocalSymbolicationService } = lazy.PerfSymbolication();
const symbolicationService = createLocalSymbolicationService(
  sharedLibraries,
  objdirs
);

We should call createLocalSymbolicationService with a list of libraries which contains libraries loaded in all processes.

We could get such a list by traversing the subprofiles in profileCaptureResult. But this would mean that we would have to parse the array buffer as JSON, which would materialize the full parsed profile in the memory of the parent process, which is slow and takes up memory.

We should investigate whether we can instead get an integrated list of all shared libraries from nsIProfiler.
In other conversations we've had recently (JS source code, source maps, JIT symbols) we've tossed around the idea to return some "supplemental" information along with the profile array buffer; we could put the integrated list in that supplemental information object.

Comment 2

[Markus Stange [:mstange]]

Julien, I think this bug would be a good place to start building out the ProfileWithInfo infrastructure: We need an nsIProfiler API which returns the profile itself as an array buffer (gzipped or not, I don't know), and along with it some JS-consumable extra info which the privileged profiler JS can look at without having to JSON-parse the entire profile. In this bug, the extra info would just be the list of shared libraries. And this extra info should be accumulated from all processes. The other processes would send it up to the parent process in the same IPC call as they send the profile JSON itself, so this IPC call will need to get a new argument with an IPC-serializable type (e.g. ProfileExtraInfo).

Would you like to take a stab at this?

Once we have this infrastructure, it'll also be used for the implementation of the JS source view, source maps, and JIT profiling.

Comment 3

[Markus Stange [:mstange]]

We can leave the Android case out of the initial implementation. When profiling Android, we currently parse the entire profile into a JS object anyway, which is covered by bug 1581963.

Comment 4

[Julien Wajsberg [:julienw]]

Yeah, I can try looking at this soon!

Comment 5

[Julien Wajsberg [:julienw]]

Attachment: Bug 1776694 - Implement move operator for SharedLibraryInfo r?mstange!

Comment 6

[Julien Wajsberg [:julienw]]

Attachment: Bug 1776694 - Return a Result object from profiler_stream_json_for_this_process r?mstange!

Depends on D170500

Comment 7

[Julien Wajsberg [:julienw]]

Attachment: Bug 1776694 - Return the library info from the JSON generation functions r?mstange!

Depends on D170501

Comment 8

[Julien Wajsberg [:julienw]]

Attachment: WIP: fixup! Bug 1776694 - Return the library info from the JSON generation functions

Depends on D170502

Comment 9

[Julien Wajsberg [:julienw]]

Attachment: Bug 1776694 - Make GrabShutdownProfile return the additional information as well r?mstange!

Depends on D170782

Comment 10

[Julien Wajsberg [:julienw]]

Attachment: Bug 1776694 - Add a method to SharedLibraryInfo that would add all the entries from another SharedLibraryInfo instance r?mstange!

Depends on D170783

Comment 11

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

Attachment: Bug 1776694 - Implement ParamTraits for shared library and additional information structs r?mstange!

Depends on D170922

Comment 12

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

Attachment: Bug 1776694 - Transfer the profile additional information from children processes to parent r?mstange!

Depends on D172552

Comment 13

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

Attachment: Bug 1776694 - Gather all the additional information from children and return it from StartGathering r?mstange!

Depends on D172553

Comment 14

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

Attachment: Bug 1776694 - Return profile with additional info from GetProfileDataAsGzippedArrayBuffer r?mstange!,emilio

Depends on D172554

Comment 15

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

Attachment: Bug 1776694 - Use the shared libraries that's provided by getProfileDataAsGzippedArrayBuffer r?mstange!

Depends on D172555

Comment 16

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0ce9f03d3142
Implement move operator for SharedLibraryInfo r=mstange
https://hg.mozilla.org/integration/autoland/rev/1d4524a65bbf
Return a Result object from profiler_stream_json_for_this_process r=mstange
https://hg.mozilla.org/integration/autoland/rev/61a720cb90f1
Return the library info from the JSON generation functions r=mstange
https://hg.mozilla.org/integration/autoland/rev/4fe9056b071b
Make GrabShutdownProfile return the additional information as well r=mstange
https://hg.mozilla.org/integration/autoland/rev/4791ee289eb6
Add a method to SharedLibraryInfo that would add all the entries from another SharedLibraryInfo instance r=mstange
https://hg.mozilla.org/integration/autoland/rev/0527899014b2
Implement ParamTraits for shared library and additional information structs r=mstange
https://hg.mozilla.org/integration/autoland/rev/c80a01cb9bc5
Transfer the profile additional information from children processes to parent r=mstange
https://hg.mozilla.org/integration/autoland/rev/700a30a5a8de
Gather all the additional information from children and return it from StartGathering r=mstange
https://hg.mozilla.org/integration/autoland/rev/479ecea2cb14
Return profile with additional info from GetProfileDataAsGzippedArrayBuffer r=mstange
https://hg.mozilla.org/integration/autoland/rev/3323b6f7c34f
Use the shared libraries that's provided by getProfileDataAsGzippedArrayBuffer r=mstange

Comment 17

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/0ce9f03d3142
https://hg.mozilla.org/mozilla-central/rev/1d4524a65bbf
https://hg.mozilla.org/mozilla-central/rev/61a720cb90f1
https://hg.mozilla.org/mozilla-central/rev/4fe9056b071b
https://hg.mozilla.org/mozilla-central/rev/4791ee289eb6
https://hg.mozilla.org/mozilla-central/rev/0527899014b2
https://hg.mozilla.org/mozilla-central/rev/c80a01cb9bc5
https://hg.mozilla.org/mozilla-central/rev/700a30a5a8de
https://hg.mozilla.org/mozilla-central/rev/479ecea2cb14
https://hg.mozilla.org/mozilla-central/rev/3323b6f7c34f