Re: [PATCH 1/7] memcg: sc.nr_to_reclaim should be initialized

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> >> 1. How far does this push pages (in terms of when limit is hit)?
> >
> > 32 pages per mem_cgroup_shrink_node_zone().
> >
> > That said, the algorithm is here.
> >
> > 1. call mem_cgroup_largest_soft_limit_node()
> >   calculate largest cgroup
> > 2. call mem_cgroup_shrink_node_zone() and shrink 32 pages
> > 3. goto 1 if limit is still exceed.
> >
> > If it's not your intention, can you please your intended algorithm?
> 
> We set it to 0, since we care only about a single page reclaim on
> hitting the limit. IIRC, in the past we saw an excessive pushback on
> reclaiming SWAP_CLUSTER_MAX pages, just wanted to check if you are
> seeing the same behaviour even now after your changes.

Actually, we have 32 pages reclaim batch size. (see nr_scan_try_batch() and related functions)
thus <32 value doesn't works as your intended.

But, If you run your test again, and (if there is) report any bugs. I'm very glad and fix it soon.

Thanks.