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Date:   Wed, 30 Jan 2019 08:17:59 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Andrea Arcangeli <aarcange@redhat.com>
Cc:     lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Peter Xu <peterx@redhat.com>,
        Blake Caldwell <blake.caldwell@colorado.edu>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
        David Rientjes <rientjes@google.com>
Subject: Re: [LSF/MM TOPIC] NUMA remote THP vs NUMA local non-THP under
 MADV_HUGEPAGE
Message-ID: <20190130071759.GR18811@dhcp22.suse.cz>
References: <20190129234058.GH31695@redhat.com>
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On Tue 29-01-19 18:40:58, Andrea Arcangeli wrote:
> Hello,
> 
> I'd like to attend the LSF/MM Summit 2019. I'm interested in most MM
> topics and it's enlightening to listen to the common non-MM topics
> too.
> 
> One current topic that could be of interest is the THP / NUMA tradeoff
> in subject.
> 
> One issue about a change in MADV_HUGEPAGE behavior made ~3 years ago
> kept floating around for the last 6 months (~12 months since it was
> initially reported as regression through an enterprise-like workload)
> and it was hot-fixed in commit
> ac5b2c18911ffe95c08d69273917f90212cf5659, but it got quickly reverted
> for various reasons.
> 
> I posted some benchmark results showing that for tasks without strong
> NUMA locality the __GFP_THISNODE logic is not guaranteed to be optimal
> (and here of course I mean even if we ignore the large slowdown with
> swap storms at allocation time that might be caused by
> __GFP_THISNODE). The results also show NUMA remote THPs help
> intrasocket as well as intersocket.
> 
> https://lkml.kernel.org/r/20181210044916.GC24097@redhat.com
> https://lkml.kernel.org/r/20181212104418.GE1130@redhat.com
> 
> The following seems the interim conclusion which I happen to be in
> agreement with Michal and Mel:
> 
> https://lkml.kernel.org/r/20181212095051.GO1286@dhcp22.suse.cz
> https://lkml.kernel.org/r/20181212170016.GG1130@redhat.com

I am definitely interested in discussing this topic and actually wanted
to propose it myself. I would add that part of the discussion was
proposing a neww memory policy that would effectively enable per-vma
node-reclaim like behavior.
-- 
Michal Hocko
SUSE Labs