Re: [PATCH] mm/rmap.c: reuse mergeable anon_vma as parent when fork

[Matthew Wilcox]

On Sat, Oct 05, 2019 at 07:48:45AM +0800, Wei Yang wrote:
> On Fri, Oct 04, 2019 at 09:11:20AM -0700, Matthew Wilcox wrote:
> >On Sat, Oct 05, 2019 at 12:06:32AM +0800, Wei Yang wrote:
> >> After this change, kernel build test reduces 20% anon_vma allocation.
> >
> >But does it have any effect on elapsed time or peak memory consumption?
> 
> Do the same kernel build test and record time:
> 
> 
> Origin
> 
> real	2m50.467s
> user	17m52.002s
> sys	1m51.953s    
> 
> real	2m48.662s
> user	17m55.464s
> sys	1m50.553s    
> 
> real	2m51.143s
> user	17m59.687s
> sys	1m53.600s    
> 
> 
> Patched
> 
> real	2m43.733s
> user	17m25.705s
> sys	1m41.791s    
> 
> real	2m47.146s
> user	17m47.451s
> sys	1m43.474s    
> 
> real	2m45.763s
> user	17m38.230s
> sys	1m42.102s    
> 
> 
> For time in sys, it reduced 8.5%.

That's compelling!