[lkml]   [2006]   [Jun]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats
Andrew Morton wrote:
> You see the problem - if one userspace package wants the tgid-stats and
> another concurrently-running one does now, what do we do? Just leave it
> enabled and run a bit slower?
> If so, how much slower? Your changelog says some potential users don't
> need the tgid-stats, but so what? I assume this patch is a performance
> thing? If so, has it been quantified?

Here are some results from running a simple program (source below) that does
10 iterations of creating and then destroying 1000 threads. On the side, another utility
kept reading the pid (+tgid if present) stats from exiting tasks.

Yes No Ovhd
user 0.14 0.15 -6%
system 1.61 1.54 +5%
elapsed 2.01 1.94 +3%

Yes = tgid stats printed on exit
No = not printed
Ovhd = (Yes-No)/No * 100

So even in this extreme case where the per-tgid stats are indeed
half of the total data, the overhead is not very significant.

As pointed out earlier, more representative cases are
- single threaded apps (e.g. make -jX) where the current
taskstats interface already optimizes by not sending redundant per-tgid stats, or
- server-type multithreaded apps where the exits are going to be relatively infrequent (due to
reuse of thread pools) so the extra per-tgid output is not going to have much impact.

I'd suggest we drop the idea of including this patch until we have data showing that
the overhead is an issue.


#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>

int n;

void *slow_exit(void *arg)
int i = (int) arg;

int main(int argc, char *argv[])
int i,rc, rep;
pthread_t *ppthread;

n = 5 ;
if (argc > 1)
n = atoi(argv[1]);

rep = 10;
if (argc > 2)
rep = atoi(argv[2]);

ppthread = malloc(n * sizeof(pthread_t));
if (ppthread == NULL) {
printf("Memory allocation failure\n");

while (rep) {
for (i=0; i<n; i++) {
rc = pthread_create(&ppthread[i], NULL,
slow_exit, (void *)i);
if (rc) {
printf("Error creating thread %d\n", i);
for (i=0; i<n; i++) {
rc = pthread_join(ppthread[i], NULL);
if (rc) {
printf("Error joining thread %d\n", i);

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2006-06-09 23:59    [W:0.191 / U:1.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site