linux-kernel - Re: [PATCH] mm: be more verbose for alloc_contig

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Message-ID: <YEYwdjvYGiZ4crMt@dhcp22.suse.cz>
Date:   Mon, 8 Mar 2021 15:11:02 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, joaodias@...gle.com
Subject: Re: [PATCH] mm: be more verbose for alloc_contig_range faliures

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
a best effort allocator. Complaining about failure is too noisy. I do
agree that some sort of easy to enable debugging is due but please let's
make it as transparent to the code as possible.
-- 
Michal Hocko
SUSE Labs