Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
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>
 <cf79e9a4-72ba-8fa0-0710-5e82a5b5e4d5@redhat.com>
 <2cb384b9-1301-59a8-f678-c67ee26053b3@oracle.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <17c958bc-d421-f48b-a07a-bf22afc32d33@redhat.com>
Date:   Thu, 4 Mar 2021 18:21:54 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.0
MIME-Version: 1.0
In-Reply-To: <2cb384b9-1301-59a8-f678-c67ee26053b3@oracle.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 04.03.21 18:20, Mike Kravetz wrote:
> On 3/4/21 1:35 AM, David Hildenbrand wrote:
>> 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.
>>
> 
> Hi David,
> 
> Sorry my above reply was too quick as I did not take a close look at
> the code/patch.  See,
> 
> https://lore.kernel.org/mm-commits/YDAbeDsG7GhV6s6B@carbon.dhcp.thefacebook.com/
> 
> This patch is actually in Andrew's tree.
> 

Oh, I missed that discussion - thanks for the pointer!

-- 
Thanks,

David / dhildenb