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Date:   Wed, 9 May 2018 13:47:12 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Huaisheng HS1 Ye <yehs1@lenovo.com>
Cc:     Randy Dunlap <rdunlap@infradead.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
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        "mgorman@techsingularity.net" <mgorman@techsingularity.net>,
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        NingTing Cheng <chengnt@lenovo.com>,
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Subject: Re: [External] [RFC PATCH v1 3/6] mm, zone_type: create ZONE_NVM and
 fill into GFP_ZONE_TABLE
Message-ID: <20180509114712.GP32366@dhcp22.suse.cz>
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On Wed 09-05-18 04:22:10, Huaisheng HS1 Ye wrote:
> 
> > On 05/07/2018 07:33 PM, Huaisheng HS1 Ye wrote:
> > > diff --git a/mm/Kconfig b/mm/Kconfig
> > > index c782e8f..5fe1f63 100644
> > > --- a/mm/Kconfig
> > > +++ b/mm/Kconfig
> > > @@ -687,6 +687,22 @@ config ZONE_DEVICE
> > >
> > > +config ZONE_NVM
> > > +	bool "Manage NVDIMM (pmem) by memory management (EXPERIMENTAL)"
> > > +	depends on NUMA && X86_64
> > 
> > Hi,
> > I'm curious why this depends on NUMA. Couldn't it be useful in non-NUMA
> > (i.e., UMA) configs?
> > 
> I wrote these patches with two sockets testing platform, and there are two DDRs and two NVDIMMs have been installed to it.
> So, for every socket it has one DDR and one NVDIMM with it. Here is memory region from memblock, you can get its distribution.
> 
>  435 [    0.000000] Zone ranges:
>  436 [    0.000000]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
>  437 [    0.000000]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
>  438 [    0.000000]   Normal   [mem 0x0000000100000000-0x00000046bfffffff]
>  439 [    0.000000]   NVM      [mem 0x0000000440000000-0x00000046bfffffff]
>  440 [    0.000000]   Device   empty
>  441 [    0.000000] Movable zone start for each node
>  442 [    0.000000] Early memory node ranges
>  443 [    0.000000]   node   0: [mem 0x0000000000001000-0x000000000009ffff]
>  444 [    0.000000]   node   0: [mem 0x0000000000100000-0x00000000a69c2fff]
>  445 [    0.000000]   node   0: [mem 0x00000000a7654000-0x00000000a85eefff]
>  446 [    0.000000]   node   0: [mem 0x00000000ab399000-0x00000000af3f6fff]
>  447 [    0.000000]   node   0: [mem 0x00000000af429000-0x00000000af7fffff]
>  448 [    0.000000]   node   0: [mem 0x0000000100000000-0x000000043fffffff]	Normal 0
>  449 [    0.000000]   node   0: [mem 0x0000000440000000-0x000000237fffffff]	NVDIMM 0
>  450 [    0.000000]   node   1: [mem 0x0000002380000000-0x000000277fffffff]	Normal 1
>  451 [    0.000000]   node   1: [mem 0x0000002780000000-0x00000046bfffffff]	NVDIMM 1
> 
> If we disable NUMA, there is a result as Normal an NVDIMM zones will be overlapping with each other.
> Current mm treats all memory regions equally, it divides zones just by size, like 16M for DMA, 4G for DMA32, and others above for Normal.
> The spanned range of all zones couldn't be overlapped.

No, this is not correct. Zones can overlap.
-- 
Michal Hocko
SUSE Labs