Date: Sat, 4 Feb 2012 23:12:15 +0000 (UTC) From: Jilles Tjoelker <jilles@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r230998 - head/bin/sh Message-ID: <201202042312.q14NCFPQ055994@svn.freebsd.org>
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Author: jilles Date: Sat Feb 4 23:12:14 2012 New Revision: 230998 URL: http://svn.freebsd.org/changeset/base/230998 Log: sh: Use vfork in a few common cases. This uses vfork() for simple commands and command substitutions containing a single simple command, invoking an external program under certain conditions (no redirections or variable assignments, non-interactive shell, no job control). These restrictions limit the amount of code executed in a vforked child. There is a large speedup (for example 35%) in microbenchmarks. The difference in buildkernel is smaller (for example 0.5%) but still statistically significant. See http://lists.freebsd.org/pipermail/freebsd-hackers/2012-January/037581.html for some numbers. The use of vfork() can be disabled by setting a variable named SH_DISABLE_VFORK. Modified: head/bin/sh/eval.c head/bin/sh/jobs.c head/bin/sh/jobs.h head/bin/sh/var.c head/bin/sh/var.h Modified: head/bin/sh/eval.c ============================================================================== --- head/bin/sh/eval.c Sat Feb 4 23:00:27 2012 (r230997) +++ head/bin/sh/eval.c Sat Feb 4 23:12:14 2012 (r230998) @@ -921,6 +921,15 @@ evalcommand(union node *cmd, int flags, if (pipe(pip) < 0) error("Pipe call failed: %s", strerror(errno)); } + if (cmdentry.cmdtype == CMDNORMAL && + cmd->ncmd.redirect == NULL && + varlist.list == NULL && + (mode == FORK_FG || mode == FORK_NOJOB) && + !disvforkset() && !iflag && !mflag) { + vforkexecshell(jp, argv, environment(), path, + cmdentry.u.index, flags & EV_BACKCMD ? pip : NULL); + goto parent; + } if (forkshell(jp, cmd, mode) != 0) goto parent; /* at end of routine */ if (flags & EV_BACKCMD) { Modified: head/bin/sh/jobs.c ============================================================================== --- head/bin/sh/jobs.c Sat Feb 4 23:00:27 2012 (r230997) +++ head/bin/sh/jobs.c Sat Feb 4 23:12:14 2012 (r230998) @@ -57,6 +57,7 @@ __FBSDID("$FreeBSD$"); #undef CEOF /* syntax.h redefines this */ #endif #include "redir.h" +#include "exec.h" #include "show.h" #include "main.h" #include "parser.h" @@ -885,6 +886,54 @@ forkshell(struct job *jp, union node *n, } +pid_t +vforkexecshell(struct job *jp, char **argv, char **envp, const char *path, int idx, int pip[2]) +{ + pid_t pid; + struct jmploc jmploc; + struct jmploc *savehandler; + + TRACE(("vforkexecshell(%%%td, %p, %d) called\n", jp - jobtab, (void *)n, + mode)); + INTOFF; + flushall(); + savehandler = handler; + pid = vfork(); + if (pid == -1) { + TRACE(("Vfork failed, errno=%d\n", errno)); + INTON; + error("Cannot fork: %s", strerror(errno)); + } + if (pid == 0) { + TRACE(("Child shell %d\n", (int)getpid())); + if (setjmp(jmploc.loc)) + _exit(exception == EXEXEC ? exerrno : 2); + if (pip != NULL) { + close(pip[0]); + if (pip[1] != 1) { + dup2(pip[1], 1); + close(pip[1]); + } + } + handler = &jmploc; + shellexec(argv, envp, path, idx); + } + handler = savehandler; + if (jp) { + struct procstat *ps = &jp->ps[jp->nprocs++]; + ps->pid = pid; + ps->status = -1; + ps->cmd = nullstr; + jp->foreground = 1; +#if JOBS + setcurjob(jp); +#endif + } + INTON; + TRACE(("In parent shell: child = %d\n", (int)pid)); + return pid; +} + /* * Wait for job to finish. Modified: head/bin/sh/jobs.h ============================================================================== --- head/bin/sh/jobs.h Sat Feb 4 23:00:27 2012 (r230997) +++ head/bin/sh/jobs.h Sat Feb 4 23:12:14 2012 (r230998) @@ -91,6 +91,7 @@ void setjobctl(int); void showjobs(int, int); struct job *makejob(union node *, int); pid_t forkshell(struct job *, union node *, int); +pid_t vforkexecshell(struct job *, char **, char **, const char *, int, int []); int waitforjob(struct job *, int *); int stoppedjobs(void); int backgndpidset(void); Modified: head/bin/sh/var.c ============================================================================== --- head/bin/sh/var.c Sat Feb 4 23:00:27 2012 (r230997) +++ head/bin/sh/var.c Sat Feb 4 23:12:14 2012 (r230998) @@ -94,6 +94,7 @@ struct var vps2; struct var vps4; struct var vvers; static struct var voptind; +struct var vdisvfork; int forcelocal; @@ -125,6 +126,8 @@ static const struct varinit varinit[] = #endif { &voptind, 0, "OPTIND=1", getoptsreset }, + { &vdisvfork, VUNSET, "SH_DISABLE_VFORK=", + NULL }, { NULL, 0, NULL, NULL } }; Modified: head/bin/sh/var.h ============================================================================== --- head/bin/sh/var.h Sat Feb 4 23:00:27 2012 (r230997) +++ head/bin/sh/var.h Sat Feb 4 23:12:14 2012 (r230998) @@ -79,6 +79,7 @@ extern struct var vppid; extern struct var vps1; extern struct var vps2; extern struct var vps4; +extern struct var vdisvfork; #ifndef NO_HISTORY extern struct var vhistsize; extern struct var vterm; @@ -109,6 +110,7 @@ extern int initial_localeisutf8; #endif #define mpathset() ((vmpath.flags & VUNSET) == 0) +#define disvforkset() ((vdisvfork.flags & VUNSET) == 0) void initvar(void); void setvar(const char *, const char *, int);
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