Constant high CPU usage

[namniav]

Issue Prelude

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Issue Details

Provide a clear description of the problem, including the following key
questions:

On M1 Macbook Air, the Terminal app, not the vim process, has constant high CPU usage for each opened C++ file, including new files that don't exist.

With 3 new empty C++ files opened, the Terminal app takes 30+% CPU usage constantly, even when there's no input/action to vim. Currently I only found this problem with C++ files and with YCM enabled. The problem disappears if no C++ file is opened(e.g. only .py files) with YCM enabled, or C++ files are opened with disabled YCM, both takes 0.0% CPU usage.

With actual C++ files with complicated source code opened, even higher CPU usage is taken for each file and heats the computer constantly.

• What did you do?

Include steps to reproduce here.

1. vim -Nu vimrc_ycm_minimal test1.cpp test2.cpp test3.cpp -O, no .cpp files have to exist.
2. Check CPU usage , no editing is needed.

If you made changes to vimrc_ycm_minimal, pase them here:

No change is made.

• What did you expect to happen?
  Don't take high CPU usage when idle.

• What actually happened?
  Terminal app takes high CPU usage constantly.

Diagnostic data

Output of vim --version

VIM - Vi IMproved 9.1 (2024 Jan 02, compiled Jun 18 2024 19:01:23)
macOS version - arm64
Included patches: 1-500
Compiled by Homebrew
Huge version without GUI.  Features included (+) or not (-):
+acl               +file_in_path      +mouse_urxvt       -tag_any_white
+arabic            +find_in_path      +mouse_xterm       -tcl
+autocmd           +float             +multi_byte        +termguicolors
+autochdir         +folding           +multi_lang        +terminal
-autoservername    -footer            -mzscheme          +terminfo
-balloon_eval      +fork()            +netbeans_intg     +termresponse
+balloon_eval_term +gettext           +num64             +textobjects
-browse            -hangul_input      +packages          +textprop
++builtin_terms    +iconv             +path_extra        +timers
+byte_offset       +insert_expand     +perl              +title
+channel           +ipv6              +persistent_undo   -toolbar
+cindent           +job               +popupwin          +user_commands
-clientserver      +jumplist          +postscript        +vartabs
+clipboard         +keymap            +printer           +vertsplit
+cmdline_compl     +lambda            +profile           +vim9script
+cmdline_hist      +langmap           -python            +viminfo
+cmdline_info      +libcall           +python3           +virtualedit
+comments          +linebreak         +quickfix          +visual
+conceal           +lispindent        +reltime           +visualextra
+cryptv            +listcmds          +rightleft         +vreplace
+cscope            +localmap          +ruby              +wildignore
+cursorbind        +lua               +scrollbind        +wildmenu
+cursorshape       +menu              +signs             +windows
+dialog_con        +mksession         +smartindent       +writebackup
+diff              +modify_fname      +sodium            -X11
+digraphs          +mouse             +sound             -xattr
-dnd               -mouseshape        +spell             -xfontset
-ebcdic            +mouse_dec         +startuptime       -xim
+emacs_tags        -mouse_gpm         +statusline        -xpm
+eval              -mouse_jsbterm     -sun_workshop      -xsmp
+ex_extra          +mouse_netterm     +syntax            -xterm_clipboard
+extra_search      +mouse_sgr         +tag_binary        -xterm_save
-farsi             -mouse_sysmouse    -tag_old_static    
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
 3rd user vimrc file: "~/.config/vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/opt/homebrew/share/vim"
Compilation: clang -c -I. -Iproto -DHAVE_CONFIG_H -DMACOS_X -DMACOS_X_DARWIN -g -O2 -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 
Linking: clang -o vim -lm -lncurses -lsodium -liconv -lintl -framework AppKit -L/opt/homebrew/opt/lua/lib -llua5.4 -mmacosx-version-min=14.2 -fstack-protector-strong -L/opt/homebrew/opt/perl/lib/perl5/5.38/darwin-thread-multi-2level/CORE -lperl -L/opt/homebrew/opt/python@3.12/Frameworks/Python.framework/Versions/3.12/lib/python3.12/config-3.12-darwin -lpython3.12 -framework CoreFoundation -lruby.3.3 -L/opt/homebrew/Cellar/ruby/3.3.3/lib 

Output of YcmDebugInfo

Printing YouCompleteMe debug information...
-- Resolve completions: Up front
-- Client logfile: /var/folders/kz/4wgytmy56ks64tslrymmc0vw0000gn/T/ycm_86u_2o90.log
-- Server Python interpreter: /opt/homebrew/opt/python@3.12/bin/python3.12
-- Server Python version: 3.12.4
-- Server has Clang support compiled in: False
-- Clang version: None
-- No extra configuration file found
-- C-family completer debug information:
--   Clangd running
--   Clangd process ID: 32966
--   Clangd executable: ['/Users/namniav/.vim/plugged/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd', '-header-insertion-decorators=0', '-resource-dir=/Users/namniav/.vim/plugged/Y
ouCompleteMe/third_party/ycmd/third_party/clang/lib/clang/17.0.1', '-limit-results=500', '-log=verbose']
--   Clangd logfiles:
--     /var/folders/kz/4wgytmy56ks64tslrymmc0vw0000gn/T/clangd_stderr_3cfrw33.log
--   Clangd Server State: Initialized
--   Clangd Project Directory: /Users/namniav/.vim/plugged/YouCompleteMe
--   Clangd Open Workspaces: {'/Users/namniav/.vim/plugged/YouCompleteMe'}
--   Clangd Settings: {}
--   Clangd Compilation Command: False
-- Server running at: http://127.0.0.1:62916
-- Server process ID: 32964
-- Server logfiles:
--   /var/folders/kz/4wgytmy56ks64tslrymmc0vw0000gn/T/ycmd_62916_stdout_33v86uc8.log
--   /var/folders/kz/4wgytmy56ks64tslrymmc0vw0000gn/T/ycmd_62916_stderr_jrmf0b2z.log
-- Semantic highlighting supported: True
-- Virtual text supported: True
-- Popup windows supported: True

Output of YcmDiags

No warnings or errors detected.

Output of git rev-parse HEAD in YouCompleteMe installation directory

b5fe27bb82cc375d66a9a006cf30390bdb215ed2

Contents of YCM, ycmd and completion engine logfiles

Reproduce the issue with vim -Nu /path/to/YCM/vimrc_ycm_minimal, which
enabled debug logging and other useful diagnostics. Include a link to a
[gist][] containing all of the log files listed by :YcmToggleLogs.
clangd_stderr_3cfrw33.log
ycm_86u_2o90.log
ycmd_62916_stderr_jrmf0b2z.log
ycmd_62916_stdout_33v86uc8.log

OS version, distribution, etc.

M1 Macbook Air, macOS 14.1 (23B74)

[puremourning]

I can't reproduce.

From the logs I can see that YCM is making the expected (small) number of server message polls

YCM has a few timers that fire every ~100ms in normal mode and ~10ms in insert mode, but these callbacks are very light.

[bstaletic]

Do we know it's vim/ycmd? Considering clangd in the debug info, I bet this is just clangd indexing a big repo which is resuling in a long high cpu load.
For LLVM I needed a few hours for clangd to index everything. After that, it was smooth sailing.

[namniav]

@puremourning Thank you for investigating the issue.
Did you start vim with -O option to open windows side by side for each file? I noticed that more vim windows(splits) for C++ files, higher constant cpu usage taken by Terminal. Without -O it's about 14% on my side.
I can reproduce the issue stably, is there something else I could try and provide?

[namniav]

Do we know it's vim/ycmd? Considering clangd in the debug info, I bet this is just clangd indexing a big repo which is resuling in a long high cpu load.

No, it's not vim/ycmd/clangd process, but only Terminal taking constant high cpu usage. It's reproducible in any empty directory on my side.

[namniav]

I just restarted macOS and it's lower but still unexpectedly high. It's about 19% with -O and 7.x% without -O.
In directory /tmp:

• YCM + CPP + -O: vim -Nu ~/.vim/plugged/YouCompleteMe/vimrc_ycm_minimal test1.cpp test2.cpp test3.cpp -O
  

• YCM + CPP: vim -Nu ~/.vim/plugged/YouCompleteMe/vimrc_ycm_minimal test1.cpp test2.cpp test3.cpp
  

• YCM + PY + -O: vim -Nu ~/.vim/plugged/YouCompleteMe/vimrc_ycm_minimal test1.py test2.py test3.py -O
  

• noYCM + CPP + -O: vim -Nu NONE test1.cpp test2.cpp test3.cpp -O
  

Edit: The columns of ActivityMonitor are same as your screenshot above: Process Name | %CPU | CPU Time | Threads | Idle Wake-Ups | Kind | %GPU