linux-kernel - Re: [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA hinting fault

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Message-ID: <CAHbLzkob_G=nNScD42-xUWJWBpOCDTTqU7F-Eg_az_MTbcgMOA@mail.gmail.com>
Date:   Thu, 1 Apr 2021 13:12:28 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Mel Gorman <mgorman@...e.de>
Cc:     Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Zi Yan <ziy@...dia.com>, Michal Hocko <mhocko@...e.com>,
        Huang Ying <ying.huang@...el.com>,
        Hugh Dickins <hughd@...gle.com>, hca@...ux.ibm.com,
        gor@...ux.ibm.com, borntraeger@...ibm.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>, linux-s390@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Gordeev <agordeev@...ux.ibm.com>
Subject: Re: [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA
 hinting fault

On Wed, Mar 31, 2021 at 6:20 AM Mel Gorman <mgorman@...e.de> wrote:
>
> On Tue, Mar 30, 2021 at 04:42:00PM +0200, Gerald Schaefer wrote:
> > Could there be a work-around by splitting THP pages instead of marking them
> > as migrate pmds (via pte swap entries), at least when THP migration is not
> > supported? I guess it could also be acceptable if THP pages were simply not
> > migrated for NUMA balancing on s390, but then we might need some extra config
> > option to make that behavior explicit.
> >
>
> The split is not done on other architectures simply because the loss
> from splitting exceeded the gain of improved locality in too many cases.
> However, it might be ok as an s390-specific workaround.
>
> (Note, I haven't read the rest of the series due to lack of time but this
> query caught my eye).

Will wait for your comments before I post v2. Thanks.

>
> --
> Mel Gorman
> SUSE Labs