[sheepdog] [PATCH v4] sheep: avoid the OOM killer

[MORITA Kazutaka]

At Fri,  5 Jul 2013 15:30:10 +0900,
Hitoshi Mitake wrote:
> 
> +int disable_oom_killing(void)
> +{
> +	int fd, ret = 0;
> +	char path[PATH_MAX], score_str[8];
> +
> +	/*
> +	 * Processes of Linux which wrote a string representation of
> +	 * OOM_SCORE_ADJ_MIN to /proc/<their pid>/oom_score_adj are excluded by
> +	 * the target list of the OOM killer certainly.
> +	 */
> +
> +	snprintf(path, PATH_MAX, "/proc/%d/oom_score_adj", getpid());

Using /proc/self/oom_score_adj is simpler.

> +	fd = open(path, O_WRONLY);
> +	if (fd < 0) {
> +		sd_eprintf("opening %s failed, %m", path);
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	snprintf(score_str, 8, "%d\n", OOM_SCORE_ADJ_MIN);

Use sizeof(score_str).

> +
> +	if (xwrite(fd, score_str, strlen(score_str)) != 6) {

Please don't use a magic number.  OOM_SCORE_ADJ_MIN is -16 on my
environment and this code doesn't work.

BTW, I wonder if we should set oom_score_adj inside the program.  I
don't how other programs disable OOM, but, perhaps, should we set this
in /etc/init.d/sheepdog?

Thanks,

Kazutaka