linux-kernel - Re: [PATCH] dma/pool: do not complain if DMA pool is not allocated

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Message-ID: <YvS727RgUrpR4ueT@dhcp22.suse.cz>
Date:   Thu, 11 Aug 2022 10:20:43 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>,
        John Donnelly <john.p.donnelly@...cle.com>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dma/pool: do not complain if DMA pool is not allocated

On Thu 11-08-22 09:28:17, Christoph Hellwig wrote:
> On Wed, Aug 03, 2022 at 11:52:10AM +0200, Michal Hocko wrote:
> > OK, so I have another machine spewing this warning. Still on an older
> > kernel but I do not think the current upstream would be any different in
> > that regards. This time the DMA zone is populated and consumed from
> > large part and the pool size request is just too large for it:
> 
> I can't really parse the last sentence.  What does "consumed from large
> part" mean here?

Meminfo part says
Node 0 DMA free:160kB boost:0kB min:0kB low:0kB high:0kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15996kB managed:15360kB mlocked:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB

So the zone has 15MB of managed memory (by the page allocator), yet only
160kB is free early boot during the allocation. So it is mostly consumed
by somebody. I haven't really checked by whom.

Does that exaplain the above better?
-- 
Michal Hocko
SUSE Labs