一次分析vim启动慢原因的经历

三个月之前，参加了牛客网和华为云的活动，实际仅花9.9元就获得了一年云服务器的使用权，此处点赞牛客网。买来肯定是要干点事情的吧，虽然花的钱不多，这其中，肯定免不了跟各种文件编辑打交道。而我作为一个vim党，配置服务器时首先要做的事情当中，自然包括安装、配置vim了。

然而，遇到一个很困惑的问题：这个服务器上的vim，启动速度太慢了。和在其他服务器、虚拟机里使用的体验完全不一样，可以明显感受到速度慢。趁着今天放假，忍无可忍，把它给解决了。

如何测量vim的启动时间？

这是摆在眼前的第一个问题，需要有数据，才好去分析。幸好，vim提供了一个参数——--startuptime，用于记录某次打开过程，各个参数、插件加载所花费的时间。以一个例子阐述下：

vim --startuptime tmp.txt ~/.vimrc

上面这条命令，会将vim打开~/.vimrc文件的启动时间（从在bash中按下回车键，到vim启动界面出现）所耗费的时间过程保存在tmp.txt文件中。


times in msec
 clock   self+sourced   self:  sourced script
 clock   elapsed:              other lines

000.003  000.003: --- VIM STARTING ---
000.095  000.092: Allocated generic buffers
000.160  000.065: locale set
000.169  000.009: GUI prepared
000.173  000.004: clipboard setup
000.175  000.002: window checked
000.598  000.423: inits 1
000.656  000.058: parsing arguments
000.657  000.001: expanding arguments
000.663  000.006: shell init
000.935  000.272: Termcap init
000.964  000.029: inits 2
001.096  000.132: init highlight
002.137  000.791  000.791: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syncolor.vim
002.238  000.940  000.149: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/synload.vim
008.792  006.523  006.523: sourcing /home/ljh/.user/local/share/vim/vim81/filetype.vim
008.842  007.603  000.140: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syntax.vim
009.200  000.165  000.165: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syncolor.vim
009.546  000.155  000.155: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syncolor.vim
009.926  000.171  000.171: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syncolor.vim
010.171  000.153  000.153: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/syncolor.vim
010.639  001.405  000.926: sourcing /home/ljh/.vim/colors/molokai.vim
012.270  001.607  001.607: sourcing /home/ljh/.vim/autoload/plug.vim
013.153  000.469  000.469: sourcing /home/ljh/.user/local/share/vim/vim81/ftoff.vim
019.308  005.606  005.606: sourcing /home/ljh/.user/local/share/vim/vim81/filetype.vim
019.390  000.038  000.038: sourcing /home/ljh/.user/local/share/vim/vim81/ftplugin.vim
019.456  000.030  000.030: sourcing /home/ljh/.user/local/share/vim/vim81/indent.vim
027.356  026.149  009.226: sourcing $HOME/.vimrc
027.362  000.117: sourcing vimrc file(s)
028.105  000.179  000.179: sourcing /home/ljh/.vim/plugged/nerdtree/autoload/nerdtree.vim
030.324  000.599  000.599: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/path.vim
030.526  000.169  000.169: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/menu_controller.vim
030.627  000.075  000.075: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/menu_item.vim
030.751  000.099  000.099: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/key_map.vim
030.997  000.222  000.222: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/bookmark.vim
031.227  000.201  000.201: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/tree_file_node.vim
031.680  000.426  000.426: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/tree_dir_node.vim
031.901  000.195  000.195: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/opener.vim
032.155  000.228  000.228: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/creator.vim
032.221  000.040  000.040: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/flag_set.vim
032.377  000.130  000.130: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/nerdtree.vim
033.510  001.108  001.108: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/ui.vim
033.567  000.020  000.020: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/event.vim
033.628  000.034  000.034: sourcing /home/ljh/.vim/plugged/nerdtree/lib/nerdtree/notifier.vim
034.109  000.450  000.450: sourcing /home/ljh/.vim/plugged/nerdtree/autoload/nerdtree/ui_glue.vim
038.206  001.715  001.715: sourcing /home/ljh/.vim/plugged/nerdtree/nerdtree_plugin/exec_menuitem.vim
038.876  000.649  000.649: sourcing /home/ljh/.vim/plugged/nerdtree/nerdtree_plugin/fs_menu.vim
038.928  000.038  000.038: sourcing /home/ljh/.vim/plugged/nerdtree/nerdtree_plugin/vcs.vim
038.995  011.492  004.915: sourcing /home/ljh/.vim/plugged/nerdtree/plugin/NERD_tree.vim
039.287  000.069  000.069: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/getscriptPlugin.vim
039.645  000.347  000.347: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/gzip.vim
039.905  000.250  000.250: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/logiPat.vim
039.945  000.029  000.029: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/manpager.vim
040.164  000.187  000.187: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/matchparen.vim
041.772  001.595  001.595: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/netrwPlugin.vim
041.858  000.042  000.042: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/rrhelper.vim
041.904  000.029  000.029: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/spellfile.vim
042.155  000.237  000.237: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/tarPlugin.vim
042.282  000.107  000.107: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/tohtml.vim
042.482  000.185  000.185: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/vimballPlugin.vim
042.675  000.166  000.166: sourcing /home/ljh/.user/local/share/vim/vim81/plugin/zipPlugin.vim
042.679  000.582: loading plugins
042.743  000.064: loading packages
042.766  000.023: loading after plugins
042.800  000.034: inits 3
043.013  000.213: reading viminfo
3410.082  3367.069: setup clipboard
3410.095  000.013: setting raw mode
3755.185  345.090: waiting for return
3755.191  000.006: start termcap
3755.214  000.023: clearing screen
3757.400  000.617  000.617: sourcing /home/ljh/.user/local/share/vim/vim81/scripts.vim
3764.045  001.058  001.058: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/lua.vim
3764.693  000.413  000.413: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/pod.vim
3767.382  003.187  002.774: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/perl.vim
3770.574  003.042  003.042: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/ruby.vim
3771.459  000.725  000.725: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/python.vim
3772.588  014.926  006.914: sourcing /home/ljh/.user/local/share/vim/vim81/syntax/vim.vim
3773.056  000.267  000.267: sourcing /home/ljh/.user/local/share/vim/vim81/ftplugin/vim.vim
3773.501  000.104  000.104: sourcing /home/ljh/.user/local/share/vim/vim81/indent/vim.vim
3773.599  002.471: opening buffers
3773.645  000.046: BufEnter autocommands
3773.647  000.002: editing files in windows
3774.170  000.523: VimEnter autocommands
3774.173  000.003: before starting main loop
3783.250  009.077: first screen update
3783.252  000.002: --- VIM STARTED ---

其中，数字第一列表示从每一项的时间戳，第二列表示该项花的具体时间，它们的单位都是毫秒（ms）。因而我们关注第二项，使用sort命令对第二列按数值，从小到大进行排序：

sort -nrk 2 tmp.txt

发现前两项太“瞩目”了：

3410.082  3367.069: setup clipboard
3755.185  345.090: waiting for return

两项加起来快4秒了，难怪会觉得那么卡！

接下来该怎么办？自然是问问神奇的咕歌同学了。
在stackoverflow上，找到了答案。
首先，通过下列命令看是否是这个原因：

vim -X --startuptime tmp-1.txt ~/.vimrc

如果加了启动参数-X后，没有了上面两项或者上面两项耗费的时间少，那就说明是下面的这个原因了。
原来，vim在启动时会去连接X Server以便它能使用剪切板（clipboard）和窗口标题。这种情况的发生需要满足三个条件：

通过终端模拟器使用vim
vim编译时加了+X11选项，开启了该特性
vim与X Server之间的连接慢

前面两个好理解，我是在Windows 10上，使用MobaXterm登录服务器的，并且由于一些需要，vim是编译安装并开启了这个特性。那第三个是为什么？我是通过ssh直接连接，并没有使用X Server呀？好叭，原来是因为MobaXterm启用了X11 Forward功能。

一次分析vim启动慢原因的经历

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