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

[Hitoshi Mitake]

At Fri, 5 Jul 2013 13:31:35 +0800,
Liu Yuan wrote:
> 
> On Fri, Jul 05, 2013 at 02:27:47PM +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>
> > ---
> >  sheep/sheep.c |   28 ++++++++++++++++++++++++++++
> >  1 file changed, 28 insertions(+)
> > 
> > diff --git a/sheep/sheep.c b/sheep/sheep.c
> > index 84bd269..ac9cc2a 100644
> > --- a/sheep/sheep.c
> > +++ b/sheep/sheep.c
> > @@ -371,6 +371,30 @@ static int create_work_queues(void)
> >  	return 0;
> >  }
> >  
> > +static int avoid_oom_killer(void)
> 
> kill_oom_killer is better?

I don't think so. The function is only for avoiding OOM killer by a
caller process. The name kill_oom_killer() implies stopping OOM killer
globally.

> 
> > +{
> > +	int fd, ret = 0;
> > +	char path[PATH_MAX];
> > +
> > +	/* Avoid oom-killer */
> 
> This comment is meaningless.

Sorry, I'll remove it later.

> 
> > +	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;
> > +	}
> > +
> > +	if (xwrite(fd, "-1000\n", 6) != 6) {
> 
> Please explain what does -1000 means why you choose it.

-1000 is OOM_SCORE_ADJ_MIN and this value is for avoiding OOM killer
certainly. I'll add a comment for describing this value in v2.

Thanks,
Hitoshi