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The LLVM Project is a collection of modular and reusable compiler and toolchain technologies.
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lldb-18 lldb-19 performance degradation #113314

Open Hexlord opened 1 month ago

Hexlord commented 1 month ago

There is a major difference in performance when debugging with lldb-18/lldb-19 over lldb-17, where our app (game) startup and teardown times increase almost tenfold (from under a second to multiple seconds).

Could be related to the slow symbol lookup in lldb-18 bug #64582 but it seems the fix is live in lldb-18/lldb-19 that we tested, so must be something else.

Not sure how we could help with resolving this, the repro steps is to just "lldb-18 " , then "run" and observe the different startup time compared to lldb-17.

Tested on lldb version 18.1.3 (slow perf), lldb version lldb 17.0.6 (fast perf).

llvmbot commented 1 month ago

@llvm/issue-subscribers-lldb

Author: Aleksandr Knorre (Hexlord)

There is a major difference in performance when debugging with lldb-18/lldb-19 over lldb-17, where our app (game) startup and teardown times increase almost tenfold (from under a second to multiple seconds). Could be related to the slow symbol lookup in lldb-18 bug #64582 but it seems the fix is live in lldb-18/lldb-19 that we tested, so must be something else. Not sure how we could help with resolving this, the repro steps is to just "lldb-18 <somebigapp>" , then "run" and observe the different startup time compared to lldb-17. Tested on lldb version 18.1.3 (slow perf), lldb version lldb 17.0.6 (fast perf).
Michael137 commented 1 month ago

What platform is this on? Any chance the project is open source and can be built to reproduce this? If you run log enable dwarf all -f /tmp/lldb.log, then reproduce the issue on lldb17 and lldb18 and attach both logs, there might be some useful info about how much work we're doing up-front parsing debug-info. Though that's just a guess. Maybe someone else has other ideas for useful logs to collect here

jimingham commented 1 month ago

What platform is this on? Any chance the project is open source and can be built to reproduce this? If you run log enable dwarf all -f /tmp/lldb.log, then reproduce the issue on lldb17 and lldb18 and attach both logs, there might be some useful info about how much work we're doing up-front parsing debug-info. Though that's just a guess. Maybe someone else has other ideas for useful logs to collect here

If you are generating logs for this, be sure to include the -T option to log enable since that will give us timestamps. Also, if you have a tool that can sample a process while it is running, taking samples of the fast and slow operations and comparing them to see what extra work is being done can also often be helpful.