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Subject: Re: [PATCH] mm/hugetlb: suppress wrong warning info when alloc
 gigantic page
To:     Mike Kravetz <mike.kravetz@oracle.com>,
        Chen Wandun <chenwandun@huawei.com>, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <20210219123909.13130-1-chenwandun@huawei.com>
 <46e76ac3-def1-80d4-14f1-61f7cd00d033@oracle.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <cf79e9a4-72ba-8fa0-0710-5e82a5b5e4d5@redhat.com>
Date:   Thu, 4 Mar 2021 10:35:48 +0100
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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