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使用strace查找Emacs啟動阻塞的原因有哪些
這篇文章給大家分享的是有關(guān)使用strace查找Emacs啟動阻塞的原因有哪些的內(nèi)容。小編覺得挺實用的，因此分享給大家做個參考，一起跟隨小編過來看看吧。
超過十年行業(yè)經(jīng)驗，技術(shù)領(lǐng)先，服務(wù)至上的經(jīng)營模式，全靠網(wǎng)絡(luò)和口碑獲得客戶，為自己降低成本，也就是為客戶降低成本。到目前業(yè)務(wù)范圍包括了：網(wǎng)站設(shè)計、成都網(wǎng)站制作，成都網(wǎng)站推廣，成都網(wǎng)站優(yōu)化，整體網(wǎng)絡(luò)托管，微信小程序定制開發(fā)，微信開發(fā)，App定制開發(fā)，同時也可以讓客戶的網(wǎng)站和網(wǎng)絡(luò)營銷和我們一樣獲得訂單和生意！
由于使用了 spacemacs 的配置，配置上比較復(fù)雜，不太想通過實驗縮減配置的方式來摸索出問題的地方。剛好最近在學習使用 strace 工具，因此決定使用 strace 來看看 Emacs 到底卡在哪里。
strace emacs --fg-daemon
輸出的內(nèi)容特別多，這里只截取卡頓前的部分內(nèi)容
readlinkat(AT_FDCWD, "/home", 0x7ffd1d3abb50, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972", 0x7ffd1d3abf00, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d", 0x7ffd1d3ac2b0, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa", 0x7ffd1d3ac660, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa/exec-path-from-shell-20180323.1904", 0x7ffd1d3aca10, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa/exec-path-from-shell-20180323.1904/exec-path-from-shell.elc", 0x7ffd1d3acdc0, 1024) = -1 EINVAL (無效的參數(shù))lseek(7, -2655, SEEK_CUR) = 1441read(7, "\n(defvar exec-path-from-shell-de"..., 4096) = 4096lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537brk(0x7507000) = 0x7507000lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537lseek(7, 5537, SEEK_SET) = 5537read(7, "230\\205\26\0\t\22\\307\\310\t!\vC\\\"\\211\24\\2"..., 4096) = 2430lseek(7, 7967, SEEK_SET) = 7967lseek(7, 7967, SEEK_SET) = 7967lseek(7, 7967, SEEK_SET) = 7967lseek(7, 7967, SEEK_SET) = 7967read(7, "", 4096) = 0close(7) = 0getpid() = 10818faccessat(AT_FDCWD, "/home/lujun9972/bin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/local/sbin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/local/bin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/bin/printf", X_OK) = 0stat("/usr/bin/printf", {st_mode=S_IFREG|0755, st_size=51176, ...}) = 0openat(AT_FDCWD, "/dev/null", O_RDONLY|O_CLOEXEC) = 7faccessat(AT_FDCWD, "/proc/5070/fd/.", F_OK) = 0faccessat(AT_FDCWD, "/proc/5070/fd/.", F_OK) = 0faccessat(AT_FDCWD, "/bin/bash", X_OK) = 0stat("/bin/bash", {st_mode=S_IFREG|0755, st_size=903440, ...}) = 0pipe2([8, 9], O_CLOEXEC) = 0rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0vfork() = 10949rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0close(9) = 0close(7) = 0read(8, "bash: \346\227\240\346\263\225\350\256\276\345\256\232\347\273\210\347\253\257\350\277\233\347\250\213\347\273"..., 16384) = 74read(8, "bash: \346\255\244 shell \344\270\255\346\227\240\344\273\273\345\212\241\346\216\247\345"..., 16310) = 35read(8, "setterm: \347\273\210\347\253\257 xterm-256color \344"..., 16275) = 51read(8, "Couldn't get a file descriptor r"..., 16224) = 56read(8, "bash: [: \357\274\232\351\234\200\350\246\201\346\225\264\346\225\260\350\241\250\350\276\276\345\274"..., 16168) = 34read(8, "Your display number is 0\n", 16134) = 25read(8, "Test whether fcitx is running co"..., 16109) = 53read(8, "Fcitx is running correctly.\n\n==="..., 16056) = 87read(8, "Launch fbterm...\n", 15969) = 17read(8, "stdin isn't a tty!\n", 15952) = 19read(8, "__RESULT\0/home/lujun9972/bin:/ho"..., 15933) = 298read(8, 0x7ffd1d39ce9d, 15635) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=10949, si_uid=1000, si_status=0, si_utime=10, si_stime=7} ---rt_sigreturn({mask=[]}) = -1 EINTR (被中斷的系統(tǒng)調(diào)用)read(8, "", 15635) = 0wait4(10949, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 10949close(8) = 0getpid() = 10818faccessat(AT_FDCWD, "/home/lujun9972/bin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/local/sbin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/local/bin/printf", X_OK) = -1 ENOENT (沒有那個文件或目錄)faccessat(AT_FDCWD, "/usr/bin/printf", X_OK) = 0stat("/usr/bin/printf", {st_mode=S_IFREG|0755, st_size=51176, ...}) = 0openat(AT_FDCWD, "/dev/null", O_RDONLY|O_CLOEXEC) = 7faccessat(AT_FDCWD, "/proc/5070/fd/.", F_OK) = 0faccessat(AT_FDCWD, "/proc/5070/fd/.", F_OK) = 0faccessat(AT_FDCWD, "/bin/bash", X_OK) = 0stat("/bin/bash", {st_mode=S_IFREG|0755, st_size=903440, ...}) = 0pipe2([8, 9], O_CLOEXEC) = 0rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0vfork() = 11679rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0close(9) = 0close(7) = 0read(8, "setterm: \347\273\210\347\253\257 xterm-256color \344"..., 16384) = 51read(8, "Couldn't get a file descriptor r"..., 16333) = 56read(8, "/home/lujun9972/.bash_profile: \347"..., 16277) = 72read(8, "Your display number is 0\nTest wh"..., 16205) = 78read(8, "Fcitx is running correctly.\n\n==="..., 16127) = 104read(8, "stdin isn't a tty!\n", 16023) = 19read(8, "__RESULT\0b269cd09e7ec4e8a115188c"..., 16004) = 298read(8, 0x7ffd1d39cba6, 15706) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11679, si_uid=1000, si_status=0, si_utime=1, si_stime=1} ---rt_sigreturn({mask=[]}) = -1 EINTR (被中斷的系統(tǒng)調(diào)用)read(8,很容易就可以看出，當 Emacs 卡頓時，它在嘗試從 8 號文件句柄中讀取內(nèi)容。
那么 8 號文件句柄在哪里定義的呢？往前看可以看到：
pipe2([8, 9], O_CLOEXEC) = 0rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0vfork() = 11679rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0close(9) = 0
可以推測出，Emacs 主進程 fork 出一個子進程（進程號為 11679），并通過管道讀取子進程的內(nèi)容。
然而，從
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11679, si_uid=1000, si_status=0, si_utime=1, si_stime=1} ---rt_sigreturn({mask=[]}) = -1 EINTR (被中斷的系統(tǒng)調(diào)用)read(8,可以看出，實際上子進程已經(jīng)退出了（父進程收到 SIGCHLD 信號），父進程確依然在嘗試從管道中讀取內(nèi)容，導致的阻塞。
而且從
read(8, "setterm: \347\273\210\347\253\257 xterm-256color \344"..., 16384) = 51read(8, "Couldn't get a file descriptor r"..., 16333) = 56read(8, "/home/lujun9972/.bash_profile: \347"..., 16277) = 72read(8, "Your display number is 0\nTest wh"..., 16205) = 78read(8, "Fcitx is running correctly.\n\n==="..., 16127) = 104read(8, "stdin isn't a tty!\n", 16023) = 19read(8, "__RESULT\0b269cd09e7ec4e8a115188c"..., 16004) = 298read(8, 0x7ffd1d39cba6, 15706) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
看到，子進程的輸出似乎是我的交互式登錄 bash 啟動時的輸出（加載了 .bash_profile）
在往前翻發(fā)現(xiàn)這么一段信息：
readlinkat(AT_FDCWD, "/home", 0x7ffd1d3abb50, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972", 0x7ffd1d3abf00, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d", 0x7ffd1d3ac2b0, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa", 0x7ffd1d3ac660, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa/exec-path-from-shell-20180323.1904", 0x7ffd1d3aca10, 1024) = -1 EINVAL (無效的參數(shù))readlinkat(AT_FDCWD, "/home/lujun9972/.emacs.d/elpa/exec-path-from-shell-20180323.1904/exec-path-from-shell.elc", 0x7ffd1d3acdc0, 1024) = -1 EINVAL (無效的參數(shù))lseek(7, -2655, SEEK_CUR) = 1441read(7, "\n(defvar exec-path-from-shell-de"..., 4096) = 4096
這很明顯是跟 exec-path-from-shell 有關(guān)啊。
通過查看 exec-path-from-shell 的實現(xiàn)，發(fā)現(xiàn) exec-path-from-shell 的實現(xiàn)原理是通過實際調(diào)啟一個 shell，然后輸出 PATH 和 MANPATH 的值的。 而且對于 bash 來說，默認的啟動參數(shù)為 -i -l（可以通過exec-path-from-shell-arguments來設(shè)置）。也就是說 bash 會作為交互式的登錄shell來啟動的，因此會加載 .bash_profile 和 .bashrc。
既然發(fā)現(xiàn)跟 exec-path-from-shell 這個包有關(guān)，而且據(jù)說這個包對 Linux 其實意義不大，那不如直接禁用掉好了。
dotspacemacs-excluded-packages '(exec-path-from-shell)
再次重啟Emacs，發(fā)現(xiàn)這次啟動速度明顯快了許多了。
感謝各位的閱讀！關(guān)于“使用strace查找Emacs啟動阻塞的原因有哪些”這篇文章就分享到這里了，希望以上內(nèi)容可以對大家有一定的幫助，讓大家可以學到更多知識，如果覺得文章不錯，可以把它分享出去讓更多的人看到吧！
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