On Tue, 16 Mar 2010 18:26:30 -0700 (PDT)
David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Fri, 12 Mar 2010, KAMEZAWA Hiroyuki wrote:
>
> > A small concern here.
> >
> > +u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
> > +{
> > + return res_counter_read_u64(&memcg->memsw, RES_LIMIT);
> > +}
> >
> > Because memory cgroup has 2 limit controls as "memory" and "memory+swap",
> > a user may set only "memory" limitation. (Especially on swapless system.)
> > Then, memcg->memsw limit can be infinite in some situation.
> >
> > So, how about this ? (just an idea after breif thinking..)
> >
> > u64 mem_cgroup_get_memsw_limit(struct mem_cgroup *memcg)
> > {
> > u64 memlimit, memswlimit;
> >
> > memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
> > memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
> > if (memlimit + total_swap_pages > memswlimit)
> > return memswlimit;
> > return memlimit + total_swap_pages;
> > }
> >
>
> I definitely trust your judgment when it comes to memcg, so this is how I
> implemented it for v4.
>
> Is the memcg->memsw RES_LIMIT not initialized to zero for swapless systems
> or when users don't set a value?
It's initalized to inifinite (-1UL).
> In other words, is this the optimal way
> to determine how much resident memory and swap that current's memcg is
> allowed?
>
I think so.
It's guaranteed that
mem->res.limit <= mem->memsw.limit
Then, only when
mem->res.limit + total_swap_pages > mem->memsw.limit
memsw.limit works.
Thanks,
-Kame
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