Infinite RAM usage

[lelongg]

I don't know if I should be opening an other issue for this since there is already several issues about RAM usage but I can't find a definitive answer.

Is this RAM usage an expected behavior of rust-analyzer or symptoms of a bug ?
The RAM usage seems to be growing through the day.

Here is some information about the project size (it's a cargo workspace of ~100 crates).

===============================================================================
 Language            Files        Lines         Code     Comments       Blanks
===============================================================================
 Rust                 1157       138605       127650          530        10425
 |- Markdown           112          701            5          623           73
 (Total)                         139306       127655         1153        10498
===============================================================================
 Total                1157       138605       127650          530        10425
===============================================================================

Installed version is 0.3.2370.

[davidbarsky]

Another issue is helpful, thanks. In terms of what could be immediately be done, disabling cache priming ("indexing") could help, but that largely defers the memory usage growth: if you're to open/visit the files in question, you'll largely end up with similar memory usage. This does mean the initial LSP requests will take longer, but if you have a large Cargo workspace but only edit a small subset of crates, this could help a bit.

As for if we're treating this as a bug: we are. We've had reports of rust-analyzer's memory usage increasing dramatically on some projects since #18964 landed, but haven't determined why some projects experience the memory usage spike. Is the code in question open-source...?

[lelongg]

Having read most of the threads about this issue, I've already disabled cachePriming on this project.

I cannot share code source but if you have specific questions about what could be special about our project, please ask.

[flodiebold]

Can you run rust-analyzer analysis-stats . on the project and report the results?

[lelongg]

I didn't find the path of the rust-analyzer binary used by the extension so I used rust-analyzer version 2025-02-24 and this is the output:

Database loaded:     47.69s, 8436minstr, 199mb (metadata 956.72ms, 55minstr, 7mb; build 44.58s, 50minstr, 379kb)
  item trees: 1185
Item Tree Collection: 655.05ms, 5895minstr, 28mb
  crates: 139, mods: 1972, decls: 41867, bodies: 37219, adts: 5249, consts: 3533
Item Collection:     90.58s, 632ginstr, 3268mb
Body lowering:       11.25s, 79ginstr, 431mb                                                                                                                                                               
  exprs: 1243598, ??ty: 583 (0%), ?ty: 204 (0%), !ty: 2068                                                                                                                                                 
  pats: 232679, ??ty: 39 (0%), ?ty: 28 (0%), !ty: 0
Inference:           203.43s, 1076ginstr, 2082mb
MIR lowering:        32.77s, 172ginstr, 465mb
Mir failed bodies: 2760 (8%)
Data layouts:        111.85ms, 637minstr, 14mb
Failed data layouts: 26 (0%)
Const evaluation:    117.89ms, 567minstr, 5mb
Failed const evals: 135 (3%)
Total:               338.99s, 1968ginstr, 6297mb

[davidbarsky]

We've recently added some new functionality to rust-analyzer that provides more detail about what is being analyzed. If you're to clone and build rust-analyzer from source using cargo xtask install --server --jemalloc --dev-rel (latest stable is fine!) and rerun analysis-stats, it'll emit more information about the shape of your project. Do you mind doing that?

[lelongg]

Here is the report with commit 432a3bc

Database loaded:     148.42s, 3313minstr, 694mb (metadata 2.59s, 1334kinstr, 6mb; build 143.94s, 81minstr, 30kb)
  item trees: 1184
  dependency lines of code: 18_462_466, item trees: 33_407
  dependency item stats: traits: 8_297, impl: 188_683, mods: 108_629, macro calls: 43_023, macro rules: 8_299
Item Tree Collection: 29.99s, 307ginstr, 5239mb
  Total Statistics:
    crates: 139, mods: 1970, decls: 41831, bodies: 37182, adts: 5246, consts: 3533
  Workspace:
    traits: 113, macro_rules macros: 29, proc_macros: 2
    lines of code: 218_310, item trees: 1_184
    usages: traits: 75, impl: 4_617, mods: 1_766, macro calls: 145, macro rules: 33
  Dependencies:
    lines of code: 18_462_466, item trees: 33_407
    declarations: traits: 8_297, impl: 188_683, mods: 108_629, macro calls: 43_023, macro rules: 8_299
Item Collection:     69.15s, 454ginstr, 8605mb
Body lowering:       7.31s, 59ginstr, 1055mb                                                                                                                                                               
  exprs: 1241663, ??ty: 613 (0%), ?ty: 196 (0%), !ty: 2068                                                                                                                                                 
  pats: 232323, ??ty: 39 (0%), ?ty: 28 (0%), !ty: 0
Inference:           207.93s, 1110ginstr, 4243mb
MIR lowering:        34.37s, 215ginstr, 658mb
Mir failed bodies: 2784 (8%)
Data layouts:        90.44ms, 331minstr, 19mb
Failed data layouts: 26 (0%)
Const evaluation:    90.82ms, 447minstr, 12mb
Failed const evals: 142 (4%)
Total:               352.95s, 2172ginstr, 8958mb

[Rudxain]

Just for reference: #19402

[Veykril]

Closing in favor of #19402

[MichaelMcDonnell]

@lelongg are you still able to reproduce it with newer versions of Rust? I had the same problem with Servo on NixOS but upgrading from Rust 1.85 to 1.86 (or 1.87) fixed it for me.