linux-kernel - Re: [RFC] mm/mremap: Remove redundant checks inside vma

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Date:   Tue, 11 Jul 2017 16:41:42 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Michal Hocko <mhocko@...nel.org>, Vlastimil Babka <vbabka@...e.cz>
Cc:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, mike.kravetz@...cle.com
Subject: Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable()

On 07/11/2017 12:46 PM, Michal Hocko wrote:
> On Tue 11-07-17 08:56:04, Vlastimil Babka wrote:
>> On 07/11/2017 08:50 AM, Michal Hocko wrote:
>>> On Tue 11-07-17 08:26:40, Vlastimil Babka wrote:
>>>> On 07/11/2017 08:03 AM, Michal Hocko wrote:
>>>>>
>>>>> Are you telling me that two if conditions cause more than a second
>>>>> difference? That sounds suspicious.
>>>>
>>>> It's removing also a call to get_unmapped_area(), AFAICS. That means a
>>>> vma search?
>>>
>>> Ohh, right. I have somehow missed that. Is this removal intentional?
>>
>> I think it is: "Checking for availability of virtual address range at
>> the end of the VMA for the incremental size is also reduntant at this
>> point."
> 
> I though this referred to this check
> 	if (vma->vm_next && vma->vm_next->vm_start < end)

No, that check is still there in the code.