linux-kernel - Re: [RFC PATCH] mm: support CONFIG_ZONE_DEVICE + CONFIG_ZONE

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Message-ID: <20160126060028.GB2053@sudip-laptop>
Date:	Tue, 26 Jan 2016 11:30:28 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Dan Williams <dan.j.williams@...el.com>, Mark <markk@...ra.co.uk>
Cc:	akpm@...ux-foundation.org, Rik van Riel <riel@...hat.com>,
	linux-nvdimm@...ts.01.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
	linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>,
	Mel Gorman <mgorman@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
	Jerome Glisse <j.glisse@...il.com>
Subject: Re: [RFC PATCH] mm: support CONFIG_ZONE_DEVICE + CONFIG_ZONE_DMA

On Mon, Jan 25, 2016 at 04:06:40PM -0800, Dan Williams wrote:
> It appears devices requiring ZONE_DMA are still prevalent (see link
> below).  For this reason the proposal to require turning off ZONE_DMA to
> enable ZONE_DEVICE is untenable in the short term.  We want a single
> kernel image to be able to support legacy devices as well as next
> generation persistent memory platforms.
> 
> Towards this end, alias ZONE_DMA and ZONE_DEVICE to work around needing
> to maintain a unique zone number for ZONE_DEVICE.  Record the geometry
> of ZONE_DMA at init (->init_spanned_pages) and use that information in
> is_zone_device_page() to differentiate pages allocated via
> devm_memremap_pages() vs true ZONE_DMA pages.  Otherwise, use the
> simpler definition of is_zone_device_page() when ZONE_DMA is turned off.
> 
> Note that this also teaches the memory hot remove path that the zone may
> not have sections for all pfn spans (->zone_dyn_start_pfn).
> 
> A user visible implication of this change is potentially an unexpectedly
> high "spanned" value in /proc/zoneinfo for the DMA zone.
> 
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Jerome Glisse <j.glisse@...il.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=110931
> Fixes: 033fbae988fc ("mm: ZONE_DEVICE for "device memory"")
> Reported-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>

It should actually be Reported-by: Mark <markk@...ra.co.uk>

Hi Mark,
Can you please test this patch available at https://patchwork.kernel.org/patch/8116991/
in your setup..

regards
sudip