Re: [RFC PATCH] mm: add a vma to vmacache when addr overlaps the vma range

[Wei Yang <richard.weiyang@gmail.com>]

On Tue, Oct 16, 2018 at 06:54:04AM -0700, Matthew Wilcox wrote:
>On Tue, Oct 16, 2018 at 09:47:12PM +0800, Wei Yang wrote:
>> Based on my understanding, this change would put more accurate vma entry in the
>> cache, which means reduce unnecessary vmacache update and vmacache find.
>> 
>> But the test result is not as expected. From the original changelog, I don't
>> see the explanation to add this non-overlap entry into the vmacache, so
>> curious about why this performs a little better than putting an overlapped
>> entry.
>
>What makes you think this performs any differently for this test-case?
>The numbers all seem to fall within a "reasonable variation" range to me.
>You're going to need to do some statistics (with a much larger sample
>size) to know whether there's any difference at all.
>

Matthew,

Thanks for your comment.

I use this test-case because I have little experience in performance
test and I see the original author lists the hit-rate improvement in
kernel build test.

I am thinking to evaluate the cache hit-rate, while I don't know how to
gather the statistic.

If you could give me some hint on the statistics gathering or a more
proper test case, I would appreciate a lot.

BTW, I don't get your point on "a much larger sample size". To map a
larger memory area? I lost at this point.

-- 
Wei Yang
Help you, Help me