linux-kernel - Re: [PATCH] mm/mm_init.c: add debug messsge for dma zone

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Date:   Thu, 8 Jun 2023 11:43:19 +0800
From:   Haifeng Xu <haifeng.xu@...pee.com>
To:     David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>
Cc:     rppt@...nel.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/mm_init.c: add debug messsge for dma zone



On 2023/6/7 18:22, David Hildenbrand wrote:
> On 07.06.23 12:16, Michal Hocko wrote:
>> On Wed 07-06-23 09:07:34, Haifeng Xu wrote:
>>> If freesize is less than dma_reserve, print warning message to report
>>> this case.
>>
>> Why?
> 
> I'd like to second that question, and add
> 
> a) Did you run into that scenario?
> b) What can an admin do in that case with that error messages?
> 
> If it reveals a buggy situation, maybe a WARN_ON_ONCE() is warranted ... but maybe only if anybody actually ran into that issue.
> 

I didn't run into that scenario, just from code review. I think the account for reserved pages is similar to memmap pages, if freesize
is less than memmap pages, it print a warning message, so for dma_reserve, it can also does the same thing.