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Message-ID: <67e0d81f-7125-455c-b02f-a9e675d55c6c@linux.alibaba.com>
Date: Tue, 6 Feb 2024 16:18:22 +0800
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Subject: Re: [RFC PATCH] mm: hugetlb: remove __GFP_THISNODE flag when
 dissolving the old hugetlb
To: Michal Hocko <mhocko@suse.com>
Cc: akpm@linux-foundation.org, muchun.song@linux.dev, osalvador@suse.de,
 david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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From: Baolin Wang <baolin.wang@linux.alibaba.com>
In-Reply-To: <ZcDvVA84s9-Azr33@tiehlicka>
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On 2024/2/5 22:23, Michal Hocko wrote:
> On Mon 05-02-24 21:06:17, Baolin Wang wrote:
> [...]
>>> It is quite possible that traditional users (like large DBs) do not use
>>> CMA heavily so such a problem was not observed so far. That doesn't mean
>>> those problems do not really matter.
>>
>> CMA is just one case, as I mentioned before, other situations can also break
>> the per-node hugetlb pool now.
> 
> Is there any other case than memory hotplug which is arguably different
> as it is a disruptive operation already.

Yes, like I said before the longterm pinning, memory failure and the 
users of alloc_contig_pages() may also break the per-node hugetlb pool.

>> Let's focus on the main point, why we should still keep inconsistency
>> behavior to handle free and in-use hugetlb for alloc_contig_range()? That's
>> really confused.
> 
> yes, this should behave consistently. And the least surprising way to
> handle that from the user configuration POV is to not move outside of
> the original NUMA node.

So you mean we should also add __GFP_THISNODE flag in 
alloc_migration_target() when allocating a new hugetlb as the target for 
migration, that can unify the behavior and avoid breaking the per-node pool?