From: Andrew Morton <akpm@linux-foundation.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Rik van Riel <riel@redhat.com>,
linux-nvdimm@ml01.01.org,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
linux-mm@kvack.org, Ingo Molnar <mingo@redhat.com>,
Mel Gorman <mgorman@suse.de>, "H. Peter Anvin" <hpa@zytor.com>,
Jerome Glisse <j.glisse@gmail.com>,
Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: Re: [RFC PATCH] mm: support CONFIG_ZONE_DEVICE + CONFIG_ZONE_DMA
Date: Tue, 26 Jan 2016 14:11:52 -0800 [thread overview]
Message-ID: <20160126141152.e1043d14502dcca17813afb3@linux-foundation.org> (raw)
In-Reply-To: <20160126000639.358.89668.stgit@dwillia2-desk3.amr.corp.intel.com>
On Mon, 25 Jan 2016 16:06:40 -0800 Dan Williams <dan.j.williams@intel.com> 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.
More than "short term". When can we ever nuke ZONE_DMA?
This was a pretty big goof - the removal of ZONE_DMA whizzed straight
past my attention, alas. In fact I never noticed the patch at all
until I got some conflicts in -next a few weeks later (wasn't cc'ed).
And then I didn't read the changelog closely enough.
> We want a single
> kernel image to be able to support legacy devices as well as next
> generation persistent memory platforms.
yup.
> 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.
Well, all these icky tricks are to avoid increasing ZONES_SHIFT, yes?
Is it possible to just use ZONES_SHIFT=3?
Also, this "dynamically added pfn of the zone" thing is a new concept
and I think it should be more completely documented somewhere in the
code.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-01-26 22:11 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-26 0:06 [RFC PATCH] mm: support CONFIG_ZONE_DEVICE + CONFIG_ZONE_DMA Dan Williams
2016-01-26 6:00 ` Sudip Mukherjee
2016-01-26 17:07 ` Dan Williams
2016-01-26 19:10 ` Mark
2016-01-26 21:42 ` Vlastimil Babka
2016-01-26 21:48 ` Dan Williams
2016-01-26 22:11 ` Andrew Morton [this message]
2016-01-26 22:33 ` Dan Williams
2016-01-26 22:51 ` Andrew Morton
2016-01-26 23:11 ` Dan Williams
2016-01-27 1:18 ` Joonsoo Kim
2016-01-27 1:37 ` Dan Williams
2016-01-27 2:15 ` Joonsoo Kim
2016-01-27 3:23 ` Dan Williams
2016-01-27 3:52 ` Joonsoo Kim
2016-01-27 4:26 ` Dan Williams
2016-01-27 5:52 ` Joonsoo Kim
2016-01-27 7:46 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160126141152.e1043d14502dcca17813afb3@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=hch@lst.de \
--cc=hpa@zytor.com \
--cc=j.glisse@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nvdimm@ml01.01.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=riel@redhat.com \
--cc=sudipm.mukherjee@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).