Re: [RESEND [PATCH] 0/2] mm/mmap.c: reduce subtree gap propagation a little

Wei Yang
2019-08-28T08:28:04Z

On Wed, Aug 28, 2019 at 10:01:40AM +0200, Vlastimil Babka wrote:
>On 8/28/19 8:06 AM, Wei Yang wrote:
>> When insert and delete a vma, it will compute and propagate related subtree
>> gap. After some investigation, we can reduce subtree gap propagation a little.
>>
>> [1]: This one reduce the propagation by update *next* gap after itself, since
>> *next* must be a parent in this case.
>> [2]: This one achieve this by unlinking vma from list.
>>
>> After applying these two patches, test shows it reduce 0.3% function call for
>> vma_compute_subtree_gap.
>
>BTW, what's the overall motivation of focusing so much
>micro-optimization effort on the vma tree lately? This has been rather
>stable code where we can be reasonably sure of all bugs being found. Now
>even after some review effort, subtle bugs can be introduced. And
>Matthew was warning for a while about an upcoming major rewrite of the
>whole data structure, which will undo all this effort?
>

Hi, Vlastimil

Thanks for your comment.

I just found there could be some refine for the code and then I modify and
test it. Hope this could help a little.

You concern is valid. The benefits / cost may be not that impressive. The
community have the final decision. For me, I just want to make it better if we
can.

--
Wei Yang
Help you, Help me