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Message-ID: <609a56e4-c8b7-154f-dcbc-a12817fb22a0@oracle.com>
Date: Wed, 30 Jan 2019 15:14:00 -0800
From: Mike Kravetz <mike.kravetz@...cle.com>
To: Andrea Arcangeli <aarcange@...hat.com>,
lsf-pc@...ts.linux-foundation.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: Peter Xu <peterx@...hat.com>,
Blake Caldwell <blake.caldwell@...orado.edu>,
Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Michal Hocko <mhocko@...nel.org>, Mel Gorman <mgorman@...e.de>,
Vlastimil Babka <vbabka@...e.cz>,
David Rientjes <rientjes@...gle.com>
Subject: Re: [LSF/MM TOPIC] NUMA remote THP vs NUMA local non-THP under
MADV_HUGEPAGE
On 1/29/19 3:40 PM, Andrea Arcangeli wrote:
> In addition to the above "NUMA remote THP vs NUMA local non-THP
> tradeoff" topic, there are other developments in "userfaultfd" land that
> are approaching merge readiness and that would be possible to provide a
> short overview about:
>
> - Peter Xu made significant progress in finalizing the userfaultfd-WP
> support over the last few months. That feature was planned from the
> start and it will allow userland to do some new things that weren't
> possible to achieve before. In addition to synchronously blocking
> write faults to be resolved by an userland manager, it has also the
> ability to obsolete the softdirty feature, because it can provide
> the same information, but with O(1) complexity (as opposed of the
> current softdirty O(N) complexity) similarly to what the Page
> Modification Logging (PML) does in hardware for EPT write accesses.
I would be interested in this topic as well. IIRC, Peter's patches do
not address hugetlbfs support. I put together patches for this some
time back. At the time, they worked as well as userfaultfd-WP support
for normal base pages: not too well :). Once base page support is
finalized, I suspect I will be involved in hugetlbfs support.
--
Mike Kravetz
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