Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [LSF/MM TOPIC] NUMA remote THP vs NUMA local non-THP under
 MADV_HUGEPAGE
To:     Andrea Arcangeli <aarcange@redhat.com>,
        lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Peter Xu <peterx@redhat.com>,
        Blake Caldwell <blake.caldwell@colorado.edu>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Michal Hocko <mhocko@kernel.org>, Mel Gorman <mgorman@suse.de>,
        Vlastimil Babka <vbabka@suse.cz>,
        David Rientjes <rientjes@google.com>
References: <20190129234058.GH31695@redhat.com>
From:   Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <609a56e4-c8b7-154f-dcbc-a12817fb22a0@oracle.com>
Date:   Wed, 30 Jan 2019 15:14:00 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.4.0
MIME-Version: 1.0
In-Reply-To: <20190129234058.GH31695@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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