linux-kernel - Re: [PATCH -mm] mm, huge page: Copy to access sub-page last when copy huge page

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Message-ID: <20180518062430.GB21711@dhcp22.suse.cz>
Date:   Fri, 18 May 2018 08:24:30 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Andi Kleen <andi.kleen@...el.com>,
        Jan Kara <jack@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>, Shaohua Li <shli@...com>,
        Christopher Lameter <cl@...ux.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: [PATCH -mm] mm, huge page: Copy to access sub-page last when
 copy huge page

On Fri 18-05-18 11:03:16, Huang, Ying wrote:
[...]
> The patch is a generic optimization which should benefit quite some
> workloads, not for a specific use case.  To demonstrate the performance
> benefit of the patch, we tested it with vm-scalability run on
> transparent huge page.

It is also adds quite some non-intuitive code. So is this worth? Does
any _real_ workload benefits from the change?

>  include/linux/mm.h |  3 ++-
>  mm/huge_memory.c   |  3 ++-
>  mm/memory.c        | 43 +++++++++++++++++++++++++++++++++++++++----
>  3 files changed, 43 insertions(+), 6 deletions(-)
-- 
Michal Hocko
SUSE Labs