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| author | jilles <jilles@FreeBSD.org> | 2012-02-04 23:12:14 +0000 |
|---|---|---|
| committer | jilles <jilles@FreeBSD.org> | 2012-02-04 23:12:14 +0000 |
| commit | c9a60ad55a7cdcf983430853a4bdb15d31340f0b (patch) | |
| tree | cdf2aa0b0a8655054be3d8275658129bb9b75c99 /bin/sh/var.h | |
| parent | a3ada8a47cbcc2eecf9773251384c95d920c9cab (diff) | |
| download | FreeBSD-src-c9a60ad55a7cdcf983430853a4bdb15d31340f0b.zip FreeBSD-src-c9a60ad55a7cdcf983430853a4bdb15d31340f0b.tar.gz | |
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.
Diffstat (limited to 'bin/sh/var.h')
| -rw-r--r-- | bin/sh/var.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/bin/sh/var.h b/bin/sh/var.h index 347c377..6cdfbfe 100644 --- a/bin/sh/var.h +++ b/bin/sh/var.h @@ -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); |
