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Subject: Re: [PATCH] mm: be more verbose for alloc_contig_range faliures
To:     Michal Hocko <mhocko@suse.com>
Cc:     Minchan Kim <minchan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, joaodias@google.com
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From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <9f7b4b8a-5317-e382-7f21-01667e017982@redhat.com>
Date:   Mon, 8 Mar 2021 15:13:35 +0100
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On 08.03.21 15:11, Michal Hocko wrote:
> On Mon 08-03-21 14:22:12, David Hildenbrand wrote:
>> On 08.03.21 13:49, Michal Hocko wrote:
> [...]
>>> Earlier in the discussion I have suggested dynamic debugging facility.
>>> Documentation/admin-guide/dynamic-debug-howto.rst. Have you tried to
>>> look into that direction?
>>
>> Did you see the previous mail this is based on:
>>
>> https://lkml.kernel.org/r/YEEUq8ZRn4WyYWVx@google.com
>>
>> I agree that "nofail" is misleading. Rather something like
>> "dump_on_failure", just a better name :)
> 
> Yeah, I have read through the email thread. I just do not get why we
> cannot make it pr_debug() and add -DDYNAMIC_DEBUG_MODULE for
> page_alloc.c (I haven't checked whether that is possible for built in
> compile units, maybe it is not but from a quick seems it should).
> 
> I really do not like this to be a part of the API. alloc_contig_range is

Which API? It does not affect alloc_contig_range() itself, it's used 
internally only. Sure, we could simply pr_debug() for each and every 
migration failure. As long as it's default-disabled, sure.

I do agree that we should look into properly including this into the 
dynamic debugging ifrastructure.

-- 
Thanks,

David / dhildenb