[sheepdog] [PATCH v2] sheep:avoid the OOM killer

[Liu Yuan]

On Fri, Jul 05, 2013 at 02:46:52PM +0900, Hitoshi Mitake wrote:
> Because sheep provides virtual disks to many VMs, sheep is an
> important process and it shouldn't be killed by the OOM killer of
> Linux. This patch implements a mechanism for avoiding the OOM killer.
> 
> Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
> ---
> 
> v2:
>  - remove the meaningless comment
>  - add a description for the value -1000
> 
>  sheep/sheep.c |   33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/sheep/sheep.c b/sheep/sheep.c
> index 84bd269..335edb4 100644
> --- a/sheep/sheep.c
> +++ b/sheep/sheep.c
> @@ -371,6 +371,35 @@ static int create_work_queues(void)
>  	return 0;
>  }
>  
> +static int avoid_oom_killer(void)
> +{
> +	int fd, ret = 0;
> +	char path[PATH_MAX];
> +
> +	snprintf(path, PATH_MAX, "/proc/%d/oom_score_adj", getpid());
> +	fd = open(path, O_WRONLY);
> +	if (fd < 0) {
> +		sd_iprintf("opening %s failed, %m", path);
> +		ret = -1;
> +		goto end;
> +	}
> +
> +	/*
> +	 * -1000 is defined as OOM_SCORE_ADJ_MIN in the linux kernel. And
> +	 * processes which wrote OOM_SCORE_ADJ_MIN to
> +	 * /proc/<their pid>/oom_score_adj are excluded by the target list of
> +	 * the OOM killer certainly.
> +	 */
> +	if (xwrite(fd, "-1000\n", 6) != 6) {
> +		sd_iprintf("writing to %s failed, %m", path);
> +		ret = -1;
> +	}

use sd_eprintf for error message please.

> +	close(fd);
> +end:

This might be a matter of taste, but since other code use label out or out_xxx
, I'd suggest use 'out' here to get more uniform view of code.

Thanks
Yuan