linux-kernel - Re: [RFC PATCH 00/25] Accelerate page migration and use memcg for PMEM management

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Message-ID: <20190404071312.GD12864@dhcp22.suse.cz>
Date:   Thu, 4 Apr 2019 09:13:12 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     ziy@...dia.com
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Keith Busch <keith.busch@...el.com>,
        Fengguang Wu <fengguang.wu@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        John Hubbard <jhubbard@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>,
        Nitin Gupta <nigupta@...dia.com>,
        Javier Cabezas <jcabezas@...dia.com>,
        David Nellans <dnellans@...dia.com>
Subject: Re: [RFC PATCH 00/25] Accelerate page migration and use memcg for
 PMEM management

On Wed 03-04-19 19:00:21, Zi Yan wrote:
> From: Zi Yan <ziy@...dia.com>
> 
> Thanks to Dave Hansen's patches, which make PMEM as part of memory as NUMA nodes.
> How to use PMEM along with normal DRAM remains an open problem. There are
> several patchsets posted on the mailing list, proposing to use page migration to
> move pages between PMEM and DRAM using Linux page replacement policy [1,2,3].
> There are some important problems not addressed in these patches:
> 1. The page migration in Linux does not provide high enough throughput for us to
> fully exploit PMEM or other use cases.
> 2. Linux page replacement is running too infrequent to distinguish hot and cold
> pages.
[...]
>  33 files changed, 4261 insertions(+), 162 deletions(-)

For a patch _this_ large you should really start with a real world
usecasing hitting bottlenecks with the current implementation. Should
microbenchmarks can trigger bottlenecks much easier but do real
application do the same? Please give us some numbers.
-- 
Michal Hocko
SUSE Labs