Tab Session Manager baloons Firefox WebExtensions process to >20GB in game replay with Stockfish in Browser on

[andreasabel]

I had to shutdown Firefox twice today since it had allocated >20GB in the WebExtensions process. I observed this behavior in game analysis mode with Stockfish in Browser on. If I do moves in game analysis mode with the client-side Stockfish for a longer time, memory consumption goes through the roof. Is the engine leaking memory?

[niklasf]

Need more to data have a chance at figuring this out.

• OS version
• Firefox version
• Which engine technology was used? (ASMJS / WASM / WASMX)
• Which settings were used? (Cores and RAM)
• How much RAM does the machine have?
• Maybe screenshots of the website, config menu and task manager

[gcp]

The WebExtensions process is where your add-ons are. Chances are much more likely you have an add-on that is leaking memory, than that there's a problem in lichess or Firefox.

The lichess.org engine runs in the Content Processes.

[gcp]

Can you take a look at about:memory, click "measure", and see if there's anything that stands out in the WebExtensions process?

[andreasabel]

I see, this might be a bad interaction with one of my add-ons. I will make a measurement next time I observe the said behavior.
Thanks!

[andreasabel]

Need more to data have a chance at figuring this out.

* OS version

macOS Mojave 10.14.6

* Firefox version

75.0 (64-bit)

* Which engine technology was used? (ASMJS / WASM / WASMX)

WASM

* Which settings were used? (Cores and RAM)

How can I modify these settings?

* How much RAM does the machine have?

Machine has 2 cores and 16 GB RAM)

* Maybe screenshots of the website, config menu and task manager

Can you take a look at about:memory, click "measure", and see if there's anything that stands out in the WebExtensions process?

Unfortunately, in the measurements it says:

WebExtensions (pid 1031)

WARNING: the 'heap-allocated' memory reporter does not work for this platform and/or configuration. This means that 'heap-unclassified' is not shown and the 'explicit' tree shows less memory than it should.

In the other sections, there are a few mentions of wasm. The runtimedoes not get credited any allocation.

0.00 MB ── wasm-runtime

However, there is one large allocation under wasm-guard-pages:

6,112.06 MB ── wasm-guard-pages

For that measurement, the "Main Process" had allocated 16GB:

16,648.20 MB (100.0%) -- explicit
├──13,729.75 MB (82.47%) ── heap-unclassified
├───1,694.07 MB (10.18%) -- dom

[niklasf]

Thanks. The settings are here, but this would have been mostly relevant for multi-threaded WASM (WASMX):

[gcp]

(WASM) guard pages don't actually use any real memory: https://bugzilla.mozilla.org/show_bug.cgi?id=1469278#c10 It may be allocated but it's not in use so it is available for other applications.

I would expect those to have been under Content Process, not WebExtensions process.

I'll check on macOS whether the details of the WebExtensions process report would help to identify what's going on there despite that warning (and if so I may ask for an additional log).

[niklasf]

Going to close, because it appear to be a general browser issue that will not require a Lichess specific solution or workaround. Please reopen if that's a wrong assessment.

[andreasabel]

I do not have the privileges to reopen.

I can only stress that this only ever and reproducibly happens with lichess.org on Firefox. Basically, I need to restart Firefox whenever I did a game replay with local Stockfish on.

[niklasf]

Can you describe why you "Need to restart Firefox"? Does it hang/freeze?

[andreasabel]

It is still the OP, quoting:

I had to shutdown Firefox twice today since it had allocated >20GB in the WebExtensions process. I observed this behavior in game analysis mode with Stockfish in Browser on. If I do moves in game analysis mode with the client-side Stockfish for a longer time, memory consumption goes through the roof. Is the engine leaking memory?

I have to restart Firefox since it has gobbled up Gigs of memory and my system responds badly because of Swap usage.

[niklasf]

Ok, so if swap is used it's not just a number, but really physical memory.

[gcp]

First thing to do would be to test with a Firefox running in safe mode, i.e. all extensions disabled. As already mentioned, if the leaking process is the WebExtensions process, that means you have an add-on that is not freeing the memory.

[andreasabel]

Thanks @gcp. Safe mode looks good so far, I'll observe it for a bit longer.
My usually enabled add-ons are:

• Adblock Plus
• I don't care about cookies
• Tab Session Manager
• Video DownloadHelper

Nothing too exotic, I'd say, but I'll have to try out disabling them one-by-one to be able to tell you more.

[andreasabel]

And the winner is....

--- TAB SESSION MANAGER

Seems like TSM has shown problematic memory behavior in other situations as well: sienori/Tab-Session-Manager#337

Still puzzling why this ballooning of TSM only occurs when I do a game replay with local Stockfish on... Maybe it tries to save too much of the state of the lichess window (shooting in the dark).

Thanks for the assistance @gcp and @niklasf !

[niklasf]

Indeed. Thank you, and thanks gcp. For now let's assume that this must be fixed in the extension, but of course I am not opposed to adding a workaround to lila, if the possibility arises.