[release/10.0] [mono][interp] Add max limit to the imported IL when inlining#122588
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jeffhandley merged 1 commit intorelease/10.0from Jan 8, 2026
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While we have some simple heuristics on whether we should inline a method or not, we have no limit on how many methods we can inline. So, if a method has 1000 callsites to methods that are inlineable, we will inline each one of them, significantly bloating the code. This is made worse by more advanced SSA optimizations, because the compilation time becomes very slow and uses a lot of memory. The limit is set as a simple upper limit on the total amount of IL code being imported as part of method compilation. This is set to a generous initial value of 1MB, since local testing showed that it is still handled decently well. The largest value obtained from running System.Runtime libtests suite is 100K. A customer provided sample was hitting 8MB of imported code, which was causing GBs of mem usage and several seconds to compile the method. In the end, all this code was discarded anyway, since it was exceeding interpreter offset limits, and we had to retry compilation with inlining disabled.
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Dec 16, 2025
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/ba-g One known and unrelated failure on tvos |
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Backport of #121580 to release/10.0
/cc @BrzVlad
Customer Impact
Mono interpreter didn't have a limit for stopping inlining. Huge methods calling methods that can be inlined would lead to even more code bloat. This can result in GBs of mem used for method compilation and seconds taking to compile the method, or simply an out of memory crash. Targets using mono interpreter (wasm + ios) can be impacted.
Regression
This behavior is not technically a regression, however it is more of a problem with more advanced compiler optimizations (added from NET9+), which end up using significantly more memory / processing time.
Testing
Tested on sample provided by customer.
Risk
Low. The fix just disables inlining after a certain code growth.