linux-kernel - Re: [PATCH] mm: hugetlb: fix hugetlb_cma_reserve() if CONFIG

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Message-ID: <20200319170152.GJ20800@dhcp22.suse.cz>
Date:   Thu, 19 Mar 2020 18:01:52 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Rik van Riel <riel@...riel.com>
Cc:     Roman Gushchin <guro@...com>, Aslan Bakirov <aslan@...com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        kernel-team@...com, linux-kernel@...r.kernel.org,
        Andreas Schaufler <andreas.schaufler@....de>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Guido Günther <agx@...xcpu.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: Re: [PATCH] mm: hugetlb: fix hugetlb_cma_reserve() if CONFIG_NUMA
 isn't set

On Thu 19-03-20 12:56:34, Rik van Riel wrote:
> On Thu, 2020-03-19 at 17:16 +0100, Michal Hocko wrote:
> > 
> > This is not the first time HAVE_MEMBLOCK_NODE_MAP has been
> > problematic.
> > I might be missing something but I really do not get why do we really
> > need it these days. As for !NUMA, I suspect we can make it generate
> > the
> > right thing when !NUMA.
> 
> We're working on a different fix now.
> 
> It looks like cma_declare_contiguous calls memblock_phys_alloc_range,
> which calls memblock_alloc_range_nid, which takes a NUMA node as one
> of its arguments.
> 
> Aslan is looking at simply adding a cma_declare_contiguous_nid, which
> also takes a NUMA node ID as an argument. At that point we can simply
> leave CMA free to allocate from anywhere in each NUMA node, which by
> default already happens from the top down.
> 
> That should be the nicer long term fix to this issue.

Yes, that sounds like a better solution. Not that I would be much
happier to have HAVE_MEMBLOCK_NODE_MAP off the table as well ;)
Ohh well, it will have to remain on my todo list for some longer.
-- 
Michal Hocko
SUSE Labs