linux-kernel - Re: [PATCH] mm/rmap.c: reuse mergeable anon

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Message-ID: <20191005011554.GQ32665@bombadil.infradead.org>
Date:   Fri, 4 Oct 2019 18:15:54 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Wei Yang <richardw.yang@...ux.intel.com>
Cc:     akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
        jglisse@...hat.com, mike.kravetz@...cle.com, riel@...riel.com,
        khlebnikov@...dex-team.ru, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/rmap.c: reuse mergeable anon_vma as parent when fork

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!