In response to http://lkml.org/lkml/2006/10/20/357 I did a poor-man's
benchmark over whether
(1) depends on BLOCK
(2) if BLOCK/endif
is faster, and surprisingly,
(1) 8.92s 8.90s 8.92s
(2) 9.19s 9.21s 9.21s
came up.
This is the `generate` script used:
#!/bin/bash
ele=50000;
for((i = 0; i < $ele; ++i)); do
echo -en "config V$i\n bool \"$i\"\n depends on BLOCK\n\n";
done >fs/big-thing1;
(
echo -en "if BLOCK\n\n";
for((i = 0; i < $ele; ++i)); do
echo -en "config V$i\n bool \"$i\"\n\n";
done;
echo -en "endif\n\n";
) >fs/big-thing2;
One of the generated file would then be included in e.g. fs/Kconfig
using a "source" statement.
This the patch:
Index: linux-2.6.19-rc4/scripts/kconfig/mconf.c
===================================================================
--- linux-2.6.19-rc4.orig/scripts/kconfig/mconf.c
+++ linux-2.6.19-rc4/scripts/kconfig/mconf.c
@@ -8,6 +8,7 @@
* i18n, 2005, Arnaldo Carvalho de Melo <[email protected]>
*/
+#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <ctype.h>
@@ -858,6 +859,27 @@ static void conf_cleanup(void)
tcsetattr(1, TCSAFLUSH, &ios_org);
}
+static void tv_delta(const struct timeval *past, const struct timeval *now,
+ struct timeval *dest)
+{
+ /* Calculates the time difference between "past" and "now" and stores the
+ result in "dest". All parameters in µs. */
+ unsigned long sec = now->tv_sec - past->tv_sec;
+ long acc = now->tv_usec - past->tv_usec;
+
+ if(acc < 0) {
+ // past: 1.5, now: 2.0, sec = 2 - 1 = 1, acc = 0 - 500000 = -500000;
+ dest->tv_sec = --sec;
+#define MICROSECOND 1000000
+ dest->tv_usec = MICROSECOND + acc;
+ } else {
+ dest->tv_sec = sec;
+ dest->tv_usec = acc;
+ }
+
+ return;
+}
+
int main(int ac, char **av)
{
struct symbol *sym;
@@ -868,9 +890,17 @@ int main(int ac, char **av)
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
+ struct timeval tv_past, tv_now, tv_diff;
+ gettimeofday(&tv_past, NULL);
+
conf_parse(av[1]);
conf_read(NULL);
+ gettimeofday(&tv_now, NULL);
+ tv_delta(&tv_past, &tv_now, &tv_diff);
+ printf("Parse time took %ld.%06ld\n", tv_diff.tv_sec, tv_diff.tv_usec);
+ exit(0);
+
sym = sym_lookup("KERNELVERSION", 0);
sym_calc_value(sym);
sprintf(menu_backtitle, _("Linux Kernel v%s Configuration"),
#<EOF>
-`J'
--
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