emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

find: use sysconf(_SC_ARG_MAX) to determine the command-line size limit

Browse Source 
The find utility uses a hardcoded value of 32 * 1024 as the limit of
the command-line length when calling 'find -exec ... {} +'. This results
in over 4 times more execve() calls than in coreutils' find.

This patch uses the limit defined in system headers.

Based on the patch by  Bartosz Golaszewski <bartekgola@gmail.com>.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2014-06-22 13:54:40 +02:00
parent 6be3a5242c
commit f92f1d0181
5 changed files with 38 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
findutils/xargs.c
View File

@@ -523,12 +523,7 @@ int xargs_main(int argc, char **argv)
argc++;
}
/* -s NUM default. fileutils-4.4.2 uses 128k, but I heasitate
* to use such a big value - first need to change code to use
* growable buffer instead of fixed one.
*/
n_max_chars = 32 * 1024;
/* Make smaller if system does not allow our default value.
/*
* The Open Group Base Specifications Issue 6:
* "The xargs utility shall limit the command line length such that
* when the command line is invoked, the combined argument
@@ -536,16 +531,15 @@ int xargs_main(int argc, char **argv)
* in the System Interfaces volume of IEEE Std 1003.1-2001)
* shall not exceed {ARG_MAX}-2048 bytes".
*/
{
long arg_max = 0;
#if defined _SC_ARG_MAX
arg_max = sysconf(_SC_ARG_MAX) - 2048;
#elif defined ARG_MAX
arg_max = ARG_MAX - 2048;
#endif
if (arg_max > 0 && n_max_chars > arg_max)
n_max_chars = arg_max;
}
n_max_chars = bb_arg_max();
if (n_max_chars > 32 * 1024)
n_max_chars = 32 * 1024;
/*
* POSIX suggests substracting 2048 bytes from sysconf(_SC_ARG_MAX)
* so that the process may safely modify its environment.
*/
n_max_chars -= 2048;
if (opt & OPT_UPTO_SIZE) {
n_max_chars = xatou_range(max_chars, 1, INT_MAX);
}