[Pkg-sysvinit-devel] Bug#775912: update-rc.d is slow due to useless fadvise call

[Bolesław Tokarski]

Package: insserv
Version: 1.14.0-5

When update-rc.d is invoked (be it as part of some service installation or 
manually), on some machines it takes much more time than anticipated. Example:

# time update-rc.d apache2 defaults
...
real    5m23.611s
user    0m0.092s
sys     0m0.088s

Running an strace -f on the update-rc.d process showed that the biggest 
slowdowns are during fadvise64 WILLNEED system call. This system call is 
supposed to be asynchronous, should let the system know that it can prefetch 
the scripts, and return immediately.

Unfortunately, this is not the case: 
https://groups.google.com/forum/#!topic/fa.linux.kernel/6jyLWFKQqQ8

Below is the patch that solves the issue. On machines with 5min+ prior run, it 
now takes 0.1s. Other machines did not incur any change in time this execution 
took. I have tested and confirmed this on both Squeeze and Wheezy. I have a 
Squeeze patch available too, if anyone's interested, though that's just 
cosmetics.

Best regards,
Bolesław Tokarski

--- insserv-1.14.0.orig/insserv.c
+++ insserv-1.14.0/insserv.c
@@ -1823,7 +1823,7 @@ static void scan_script_locations(const
                continue;
            }

-           lsb = scan_script_defaults(dfd, d->d_name, override_path, &name, 
true, ignore);
+           lsb = scan_script_defaults(dfd, d->d_name, override_path, &name, 
false, ignore);
            if (!name) {
                warn("warning: script is corrupt or invalid: %s/%s%s\n", path, 
rcd, d->d_name);
                continue;
@@ -2627,7 +2627,7 @@ int main (int argc, char *argv[])
        const char *const name = argv[c];
        service_t * first = (service_t*)0;
        char * provides, * begin, * token;
-       const uchar lsb = scan_script_defaults(dfd, name, override_path, 
(char**)0, true, ignore);
+       const uchar lsb = scan_script_defaults(dfd, name, override_path, 
(char**)0, false, ignore);

        if ((lsb & FOUND_LSB_HEADER) == 0) {
            if ((lsb & (FOUND_LSB_DEFAULT|FOUND_LSB_OVERRIDE)) == 0)