On Thu, Feb 4, 2010 at 5:44 PM, Ted Unangst <[email protected]> wrote:
> I haven't really solved the problem I want to solve, but was able to whip
> this up pretty quickly. Basically, it's just a wrapper that runs a
> command and then starves it from running. disknice is a misnomer, it also
> gets starved from cpu, but at the current time the only way to slow down a
> process's io is to stop it. Not a complete solution, but it will slow
> down a large tar job to the point where other programs have plenty of time
> to get their requests in. The sleep ratios should be tunable, aren't.
>
>
>> time disknice md5 -t
> MD5 time trial. Processing 10000 10000-byte blocks...
> Digest = 52e5f9c9e6f656f3e1800dfa5579d089
> Time = 3.339803 seconds
> Speed = 29941885.793863 bytes/second
> 0m3.50s real 0m0.30s user 0m0.00s system
>
>
> #include <sys/types.h>
> #include <sys/wait.h>
>
> #include <signal.h>
> #include <stdlib.h>
> #include <unistd.h>
>
> int
> main(int argc, char **argv)
> {
> int i;
> char **nargv;
> pid_t pid;
> int status;
> const int onesec = 1000000;
>
> nargv = malloc((sizeof(*nargv) * argc + 1));
> for (i = 1; i < argc; i++) {
> nargv[i-1] = argv[i];
> }
> nargv[i-1] = NULL;
>
> pid = fork();
> if (pid == -1)
> err(127, "fork");
> if (!pid) {
> execvp(nargv[0], nargv);
> write(2, "failed to exec\n", 15);
> _exit(127);
> }
> usleep(10);
> while (!waitpid(pid, &status, WNOHANG)) {
> kill(pid, SIGSTOP);
> usleep(onesec / 2);
> kill(pid, SIGCONT);
> usleep(onesec / 10);
> }
> return WEXITSTATUS(status);
> }
>
>
May I suggest this diff:
--- disknice.c.orig Fri Feb 05 10:02:49 2010
+++ disknice.c Fri Feb 05 10:03:32 2010
@@ -13,13 +13,9 @@
pid_t pid;
int status;
const int onesec = 1000000;
-
- nargv = malloc((sizeof(*nargv) * argc + 1));
- for (i = 1; i < argc; i++) {
- nargv[i-1] = argv[i];
- }
- nargv[i-1] = NULL;
-
+
+ nargv=&argv[1];
+
pid = fork();
if (pid == -1)
err(127, "fork");
I think those lines represent a rather inefficient way of doing that,
not to mention a memory leak. You get the same effect by shifting
argv along by one, without having to dabble in allocating memory and
the like.
--
Aaron Mason - Programmer, open source addict
I've taken my software vows - for beta or for worse
