linux-kernel - Re: [PATCH] mm: Reduce memory bloat with THP

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Date:   Fri, 15 Dec 2017 23:21:46 -0800
From:   Nitin Gupta <nitin.m.gupta@...cle.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-mm@...ck.org, steven.sistare@...cle.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
        Nadav Amit <namit@...are.com>,
        Minchan Kim <minchan@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        SeongJae Park <sj38.park@...il.com>, Shaohua Li <shli@...com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Rik van Riel <riel@...hat.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Jan Kara <jack@...e.cz>, Dave Jiang <dave.jiang@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Matthew Wilcox <willy@...ux.intel.com>,
        Hugh Dickins <hughd@...gle.com>, Tobin C Harding <me@...in.cc>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: Reduce memory bloat with THP

On 12/15/17 2:01 AM, Kirill A. Shutemov wrote:
> On Thu, Dec 14, 2017 at 05:28:52PM -0800, Nitin Gupta wrote:
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index 751e97a..b2ec07b 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -508,6 +508,7 @@ static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
>>  					unsigned long start, unsigned long end)
>>  {
>>  	zap_page_range(vma, start, end - start);
>> +	vma->space_efficient = true;
>>  	return 0;
>>  }
>>  
> 
> And this modifies vma without down_write(mmap_sem).
> 

I thought this function was always called with mmmap_sem write locked.
I will check again.

- Nitin