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

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Message-ID: <2cb384b9-1301-59a8-f678-c67ee26053b3@oracle.com>
Date:   Thu, 4 Mar 2021 09:20:23 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     David Hildenbrand <david@...hat.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 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.
-- 
Mike Kravetz