linux-kernel - Re: [PATCH 1/2] mm: thp: relax __GFP_THISNODE for MADV

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Date:   Wed, 17 Oct 2018 09:08:25 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrea Argangeli <andrea@...nel.org>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>,
        "Kirill A. Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Stable tree <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm: thp:  relax __GFP_THISNODE for MADV_HUGEPAGE
 mappings

On Tue 16-10-18 16:16:43, Andrew Morton wrote:
> On Tue, 16 Oct 2018 19:11:49 -0400 Andrea Arcangeli <aarcange@...hat.com> wrote:
> 
> > This was a severe regression
> > compared to previous kernels that made important workloads unusable
> > and it starts when __GFP_THISNODE was added to THP allocations under
> > MADV_HUGEPAGE. It is not a significant risk to go to the previous
> > behavior before __GFP_THISNODE was added, it worked like that for
> > years.@s1@s2@s1
> 
> 5265047ac301 ("mm, thp: really limit transparent hugepage allocation to
> local node") was April 2015.  That's a long time for a "severe
> regression" to go unnoticed?

Well, it gets some time to adopt changes in enterprise and we start
seeing people reporting this issue. That is why I believe we should
start with something really simple and stable tree backportable first
and then build something more complex on top.
-- 
Michal Hocko
SUSE Labs