linux-kernel - Re: [RFC PATCH 0/2] mm: fix OOMs for binding workloads to movable zone only node

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Message-ID: <20201104075819.GA10052@dhcp22.suse.cz>
Date:   Wed, 4 Nov 2020 08:58:19 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>, dave.hansen@...el.com,
        ying.huang@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] mm: fix OOMs for binding workloads to movable
 zone only node

On Wed 04-11-20 15:38:26, Feng Tang wrote:
[...]
> > Could you be more specific about the usecase here? Why do you need a
> > binding to a pure movable node? 
> 
> One common configuration for a platform is small size of DRAM plus huge
> size of PMEM (which is slower but cheaper), and my guess of their use
> is to try to lead the bulk of user space allocation (GFP_HIGHUSER_MOVABLE)
> to PMEM node, and only let DRAM be used as less as possible. 

While this is possible, it is a tricky configuration. It is essentially 
get us back to 32b and highmem...

As I've said in reply to your second patch. I think we can make the oom
killer behavior more sensible in this misconfigured cases but I do not
think we want break the cpuset isolation for such a configuration.
-- 
Michal Hocko
SUSE Labs