linux-kernel - Re: [PATCH] mm: Don't fault around userfaultfd-registered regions on reads

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Date:   Fri, 27 Nov 2020 18:00:44 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: Re: [PATCH] mm: Don't fault around userfaultfd-registered regions on
 reads

On 26.11.20 23:23, Peter Xu wrote:
> Faulting around for reads are in most cases helpful for the performance so that
> continuous memory accesses may avoid another trip of page fault.  However it
> may not always work as expected.
> 
> For example, userfaultfd registered regions may not be the best candidate for
> pre-faults around the reads.

Are we getting uffd faults even though no-one actually accessed it? So
in case I would track what some part of my program actually reads, I
would get wrong notifications?

-- 
Thanks,

David / dhildenb