[UE5][Linux] Starting with the LLDB attached is very slow.

Same problem here.

BTW, how to check which version lldb is?

Hello,

Thank you for contacting Rider support.

JetBrainsBest , please try the following: Open the ~/.lldbinit file and add the row settings set symbols.load-on-demand true (fixed a typo). Save a file and try to start debug again. That should speed debugger startup time noticeably.

Eryk Dykiel , I verified the case you shared (compared Rider bundled lldb with another version (I tried this lldb 18 installed using wget https://apt.llvm.org/llvm.sh→sudo llvm.sh 18, but didn't get such a (3.5x) performance improvement. 

(note: I made Rider Rider to use standalone lldb installation instead of bundled binaries, using replacing Riders lldb binaries with softlinks, together with lib/liblldb.so)

In fact, using settings set symbols.load-on-demand true (fixed a typo) does speed up the debug startup time by 3.5x (35 seconds against ~110 seconds).

We will discuss and consider whether we want to enable this option by default in RIDER-106035.

Meantime, I would appreciate it if you could elaborate on the way you made your experiment:

• How did you replace Rider's lldb binaries with system ones;
• That would be great if you could share a recording that demonstrates your experiment;
• When you hit a breakpoint in Rider, go to Debugger output( LLDB Console), invoke settings show symbols.load-on-demand and share the output. I suppose you already have this option turned on.

Have a nice day!

Hi, Dmitry-Kazantsev

Thanks a lot for following issues on Linux!

I just tested the option you mentioned, but unfortunately It's basically making no difference for me. I've attached a image to show this.

Looks like the option didn't be read.

Looks like my image has issues to upload.

State it in text: after enabling and disabling the option, the load time from clicking the green debug button to be able to see the editor window took about 2.5 mins.

Hi,

After add “settings set symbols.load-on-demand true” rather than “settings show symbols.load-on-demand true”, I got about 2-3 times faster when start debugging.

My .lldbinit file:

```

settings set target.inline-breakpoint-strategy always

settings set symbols.load-on-demand true

command script import “/home/YOUR_PATH_TO/UnrealEngine/Engine/Extras/LLDBDataFormatters/UEDataFormatters_2ByteChars.py”

settings show symbols.load-on-demand

settings show target.inline-breakpoint-strategy

```

the “show” command would print the relevant value in “debugger output (LLDB)” window on startup.

Thank you a lot!

Hello JetBrainsBest ,

Ah, I made a typo, for sure. Take my apologies. I wanted to say settings set symbols.load-on-demand true should be added to ~/.lldbinit. Not settings show symbols.load-on-demand.

You may remove settings show symbols.load-on-demand from the lldbinit file.

Additionally, you might want to try adding this extra setting to .lldbinit: settings set symbols.enable-lldb-index-cache true. As per my tests, it speeds up startup time by 4-7 seconds (not that significantly, but still).

I am glad to hear I was able to help.

Have a nice day!

Hi Dmitry, I just tried to reproduce my previous results but with the latest version of Rider ( 2024.2.5 ). When updating to 2024.2.5 I was prompted about conflicting lldb files, previous incremental updates didn't show any popups so I assume something changed this time around on your side. Anyway I did a clean Rider install to make sure results are reliable.  I can no longer reproduce 75s startup, both “stock” rider and modified version ( with lldb replaced ) start in about ~29s. I no longer have the original project so time is not exactly apples to apples. When I originally found the issue I tried going back and forth multiple times and it was very easy to reproduce.

Since I can't reproduce the issue I'm going to skip the recording, given your description I would say you did the exact same thing as me. The only difference was that I compiled my lldb from source locally.

By the way, my original goal with replacing the lldb was to profile it to see what is taking the time. Here is a screenshot from this test ( with replaced lldb because I don't have symbols for the stock version ). Perhaps there is a chance to take it few seconds lower? :D Same project without debugger attached starts in ~15s for me.

Hello,

Thank you for the timeline shared. A several-second speedup improvement(3-6 seconds per my tests) might be got by enabling another lldb setting. You might want to give it a try: settings set symbols.enable-lldb-index-cache true (add it to ~/.lldbinit in the same way)

I submitted this another feature request to our tracker: RIDER-118280 Bring lldb-index-cache settings to Rider settings.

Have a nice day!

Looks like enable-lldb-index-cache lowers the load time by another ~3s, so down to ~26s, neat. Thanks for pointing it out again, I forgot to check it the last time.