find: use sysconf(_SC_ARG_MAX) to determine the command-line size limit
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>
diff --git a/findutils/find.c b/findutils/find.c
index 493f72e..56a7ed3 100644
--- a/findutils/find.c
+++ b/findutils/find.c
@@ -419,6 +419,7 @@
smallint need_print;
smallint xdev_on;
recurse_flags_t recurse_flags;
+ IF_FEATURE_FIND_EXEC_PLUS(unsigned max_argv_len;)
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
@@ -428,6 +429,7 @@
/* we have to zero it out because of NOEXEC */ \
memset(&G, 0, sizeof(G)); \
IF_FEATURE_FIND_MAXDEPTH(G.minmaxdepth[1] = INT_MAX;) \
+ IF_FEATURE_FIND_EXEC_PLUS(G.max_argv_len = bb_arg_max() - 2048;) \
G.need_print = 1; \
G.recurse_flags = ACTION_RECURSE; \
} while (0)
@@ -677,7 +679,7 @@
ap->file_len += strlen(fileName) + sizeof(char*) + 1;
/* If we have lots of files already, exec the command */
rc = 1;
- if (ap->file_len >= 32*1024)
+ if (ap->file_len >= G.max_argv_len)
rc = do_exec(ap, NULL);
return rc;
}
diff --git a/findutils/xargs.c b/findutils/xargs.c
index 0ba5b56..76c4747 100644
--- a/findutils/xargs.c
+++ b/findutils/xargs.c
@@ -523,12 +523,7 @@
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 @@
* 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);
}
diff --git a/include/libbb.h b/include/libbb.h
index a1a0dc1..fa69a7f 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -731,6 +731,14 @@
/* Never returns NULL */
extern void *xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p) FAST_FUNC RETURNS_MALLOC;
+#if defined ARG_MAX
+# define bb_arg_max() ((unsigned)ARG_MAX)
+#elif defined _SC_ARG_MAX
+unsigned bb_arg_max(void) FAST_FUNC;
+#else
+# define bb_arg_max() ((unsigned)(32 * 1024))
+#endif
+
#define SEAMLESS_COMPRESSION (0 \
|| ENABLE_FEATURE_SEAMLESS_XZ \
|| ENABLE_FEATURE_SEAMLESS_LZMA \
diff --git a/libbb/Kbuild.src b/libbb/Kbuild.src
index 6578d11..62680bd 100644
--- a/libbb/Kbuild.src
+++ b/libbb/Kbuild.src
@@ -92,6 +92,7 @@
lib-y += speed_table.o
lib-y += str_tolower.o
lib-y += strrstr.o
+lib-y += sysconf.o
lib-y += time.o
lib-y += trim.o
lib-y += u_signal_names.o
diff --git a/libbb/sysconf.c b/libbb/sysconf.c
new file mode 100644
index 0000000..c5fa5e0
--- /dev/null
+++ b/libbb/sysconf.c
@@ -0,0 +1,16 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Various system configuration helpers.
+ *
+ * Copyright (C) 2014 Bartosz Golaszewski <bartekgola@gmail.com>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+#include "libbb.h"
+
+#if defined _SC_ARG_MAX
+unsigned FAST_FUNC bb_arg_max(void)
+{
+ return sysconf(_SC_ARG_MAX);
+}
+#endif