不知道从哪个版本开始,macOS 最大文件数(max open files)改成了 1024,这对于使用 lsp 进行开发来说,显得有些小。而且这个问题并不能简单通过调大 ulimit 解决,在这个 reddit 帖子[1]里,rpluim 用户提到:
Emacs uses pselect, which is limited to FD_SETSIZE file descriptors, usually 1024. I suspect you've got one of the file-watching utilities enabled in emacs, which tends to use up a lot of file descriptors. … Increasing the maxfiles limit will not change the value of FD_SETSIZE compiled into emacs and the macOS libraries. Emacs would have to move to using poll or kqueue to fully solve this issue.
在 macOS 的开发者文档[2]里也能找到印证:
The default size FD_SETSIZE (currently 1024) is some-what somewhat what smaller than the current kernel limit to the number of open files. However, in order to accommodate programs which might potentially use a larger number of open files with select, it is possible to increase this size within a program by providing a larger definition of FD_SETSIZE before the inclusion of <sys/types.h>.
但是文档里没提到怎么改,搜了下找到了一个 erlang 的类似问题[3],里面有提到怎么修改:
CFLAGS="-DFD_SETSIZE=10000 -DDARWIN_UNLIMITED_SELECT"
Great!经过一番测试,成功将 emacs 的最大文件数改成 10000,这里总结下步骤:
limit.maxfiles.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>limit.maxfiles</string>
<key>ProgramArguments</key>
<array>
<string>launchctl</string>
<string>limit</string>
<string>maxfiles</string>
<string>64000</string>
<string>524288</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>ServiceIPC</key>
<false/>
</dict>
</plist>
上面的 xml 含义是把最大文件打开数的 soft/hard 限制分别改成 64000 与 524288。
sudo chown root:wheel /Library/LaunchDaemons/limit.maxfiles.plist
sudo chmod 644 /Library/LaunchDaemons/limit.maxfiles.plist
# 加载plist文件
sudo launchctl load -w /Library/LaunchDaemons/limit.maxfiles.plist
# 确认已经生效
launchctl limit maxfiles
ulimit -n
git clone https://git.savannah.gnu.org/emacs && cd emacs
git checkout emacs-28
git clean -xf
./autogen.sh
./configure "CFLAGS=-DFD_SETSIZE=10000 -DDARWIN_UNLIMITED_SELECT"
export CPATH=`xcrun --show-sdk-path`/usr/include:`xcrun --show-sdk-path`/usr/include/libxml2
make -j 4 && make install
之后打开新编译的 Emacs 进行测试:
(shell-command-to-string "ulimit -n")
;; 10000
(dotimes (i 2000)
(make-process
:name (format "Sleep-%s" i)
:buffer nil
:command '("sleep" "60000")
:connection-type 'pipe))
上面的 dotimes
代码块创建了 2000 个进程,之后用 lsof -p ${emacs_pid} | wc -l
查看打开的文件数,可以看到是 4000 多个,应该是一个 process 会打开两个文件:stdout 与 stderr。
这样,Emacs 最大文件打开数就成功修改了!
[1]
这个 reddit 帖子: https://www.reddit.com/r/emacs/comments/mq2znn/comment/gudivjv/?utm_source=share&utm_medium=web2x&context=3
[2]
开发者文档: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/select.2.html
[3]
类似问题: https://github.com/Homebrew/legacy-homebrew/issues/6143
[4]
这个 gist: https://gist.github.com/skylock/0117ec637d468f91260927b43b816eda
[5]
Mac OS X下的资源限制: https://wudaijun.com/2017/02/max-osx-ulimit/