clangd can use all system memory, including up to 64 gigabytes of ram

[jbwyatt4]

Copying and pasting this issue report from this link: https://github.com/nvim-lua/kickstart.nvim/issues/773

Describe the bug To Reproduce

1) Please download the Linux kernel source 2) Build a kernel for the LSP as documented here: https://gitlab.com/jbwyatt4/vim-megarepo/-/blob/main/neo-elk/Workflow.md?ref_type=heads 3) Go to any .c file, the indexer, clangd, may take up to the full system memory (which on my system is 64 gigabytes of ram) and cause an out of memory situation or be killed by an OOM killer.

Desktop

OS: Fedora 39
Terminal: Version 3.50.1 for GNOME 45
A terminal emulator for the GNOME desktop
Using VTE version 0.74.2 +BIDI +GNUTLS +ICU +SYSTEMD

Neovim Version

NVIM v0.9.5
Build type: RelWithDebInfo
LuaJIT 2.1.1692716794
Compilation: /usr/bin/gcc -O2 -g -Og -g -Wall -Wextra -pedantic -Wno-unused-para
meter -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion -Wvla -Wdouble-promot
ion -Wmissing-noreturn -Wmissing-format-attribute -Wmissing-prototypes -fno-comm
on -Wno-unused-result -Wimplicit-fallthrough -fdiagnostics-color=auto -fstack-pr
otector-strong -DUNIT_TESTING -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DU
SING_UV_SHARED=1 -I/usr/include/luajit-2.1 -I/usr/include -I/usr/include/luv -I/
builddir/build/BUILD/neovim-0.9.5/redhat-linux-build/src/nvim/auto -I/builddir/b
uild/BUILD/neovim-0.9.5/redhat-linux-build/include -I/builddir/build/BUILD/neovi
m-0.9.5/redhat-linux-build/cmake.config -I/builddir/build/BUILD/neovim-0.9.5/src
 -I/usr/include -I/usr/include -I/usr/include -I/usr/include -I/usr/include -I/u
sr/include -I/usr/include

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/share/nvim"

This has been going on for a while. How do I limit the memory it uses in Neovim? I would to limit the indexer to 2 or 8 gigs of memory. I checked the documentation on memory, but I am not sure of how to use it to limit it. https://clangd.llvm.org/extensions#memory-usage

My config:

https://gitlab.com/jbwyatt4/vim-megarepo/-/blob/dev/neo-elk/init.lua?ref_type=heads

[p00f]

The memory usage feature is just for viewing where the memory is used.

LLVM and Chromium have online indexes (updated nightly or so), you can see if there's one for the kernel: https://clangd.llvm.org/design/remote-index

[p00f]

You can use cgroups to limit memory usage

[jbwyatt4]

What command with cgroups would you use to limit memory usage? I would like something that is very automated.

LLVM and Chromium have online indexes (updated nightly or so), you can see if there's one for the kernel: https://clangd.llvm.org/design/remote-index

This talks about project wide indexes, but not the LLVM or Chromium ones. Do you have links to those?

[jbwyatt4]

If you are talking about the compile_commands.json you generate it with this:

https://gitlab.com/jbwyatt4/vim-megarepo/-/blob/dev/neo-elk/Workflow.md?ref_type=heads#building-the-compile_commandsjson-for-the-upstream-kernel

[p00f]

What command with cgroups would you use to limit memory usage

One-time setup 1) ~/.config/systemd/user/clangd.slice:

[Slice]
MemoryMax=2G

2) systemctl --user daemon-reload

Then, systemd-run --user --slice=clangd.slice clangd

This talks about project wide indexes, but not the LLVM or Chromium ones. Do you have links to those?

https://linux.clangd-index.chromium.org/, https://clangd-index.llvm.org/

If you are talking about the compile_commands.json

?

[p00f]

To automate this, you can use 'exrc' - in the kernel repo, create a .nvim.lua which starts clangd under the slice

[p00f]

Or you could check the cwd when calling vim.lsp.start and change the cmd based on that.

[p00f]

You also need to add --pty to the systemd-run command as the server works over stdio

systemd-run --user --slice=clangd.slice --pty clangd

[p00f]

[jbwyatt4]

Thank you @p00f. I went with the clangd.slice option. I did not need to reload the systemd service as it seems to terminate itself when Neovim is not in use for the way my bundle distribution is setup.

There is still one more problem but I will open another issue for it. Closing this issue.

[p00f]

Yes, with --pty it's like a normal terminal application, it is not backgrounded like a systemd service