linux-kernel - Re: [PATCH] mm/hugetlb: suppress wrong warning info when alloc gigantic page

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Message-ID: <cf79e9a4-72ba-8fa0-0710-5e82a5b5e4d5@redhat.com>
Date:   Thu, 4 Mar 2021 10:35:48 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Chen Wandun <chenwandun@...wei.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: suppress wrong warning info when alloc
 gigantic page

On 19.02.21 20:14, Mike Kravetz wrote:
> On 2/19/21 4:39 AM, Chen Wandun wrote:
>> If hugetlb_cma is enabled, it will skip boot time allocation
>> when allocating gigantic page, that doesn't means allocation
>> failure, so suppress this warning info.
>>
> 
> Normally the addition of warning messages is discouraged.  However, in
> this case the additional message provides value.  Why?
> 
> Prior to the commit cf11e85fc08c, one could have a kernel command line
> that contains:
> 
> hugepagesz=1G hugepages=16
> 
> This would allocate 16 1G pages at boot time.
> 
> After the commit, someone could specify a command line containing:
> 
> hugepagesz=1G hugepages=16 hugetlb_cma=16G
> 
> In this case, 16G of CMA will be reserved for 1G huge page allocations
> after boot time.  The parameter 'hugepages=16' is ignored, and the warning
> message is logged.  The warning message should only be logged when the
> kernel parameter 'hugepages=' is ignored.
> 
> IMO, it make sense to log a warning if ignoring a user specified parameter.
> The user should not be attempting boot time allocation and CMA reservation
> for 1G pages.
> 
> I do not think we should drop the warning as the it tells the user thay
> have specified two incompatible allocation options.
> 

I agree. It has value.

-- 
Thanks,

David / dhildenb