linux-kernel - Re: [LSF/MM TOPIC] NUMA remote THP vs NUMA local non-THP under MADV

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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