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Date: Tue, 8 Oct 2019 17:47:06 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Subject: Re: [PATCH v5 01/11] asm-generic/pgtable: Adds generic functions to
 monitor lockless pgtable walks
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On Sat, Oct 05, 2019 at 02:05:29PM +0530, Aneesh Kumar K.V wrote:
> MADV_DONTNEED has caused us multiple issues due to the fact that it can run
> in parallel to page fault. I am not sure whether we have a known/noticeable
> performance gain in allowing that with mmap_sem held in read mode.

Yes we do. MADV_DONTNEED used a lot by userspace memory allocators and it
will be very noticible performance regression if we would switch it to
down_write(mmap_sem).

-- 
 Kirill A. Shutemov