Re: [RFC] mm/mremap: Remove redundant checks inside vma_expandable()

[Vlastimil Babka]

On 07/11/2017 08:03 AM, Michal Hocko wrote:
> On Tue 11-07-17 09:58:42, Anshuman Khandual wrote:
>>> here. This is hardly something that would save many cycles in a
>>> relatively cold path.
>>
>> Though I have not done any detailed instruction level measurement,
>> there is a reduction in real and system amount of time to execute
>> the test with and without the patch.
>>
>> Without the patch
>>
>> real	0m2.100s
>> user	0m0.162s
>> sys	0m1.937s
>>
>> With this patch
>>
>> real	0m0.928s
>> user	0m0.161s
>> sys	0m0.756s
> 
> 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?