From: Grant Likely <grant.likely@secretlab.ca>
To: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Rob Herring <robherring2@gmail.com>,
Deepak Saxena <dsaxena@linaro.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Scott Wood <scottwood@freescale.com>,
Tony Lindgren <tony@atomide.com>, Russ Dill <Russ.Dill@ti.com>,
Felipe Balbi <balbi@ti.com>, Benoit Cousson <b-cousson@ti.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Koen Kooi <koen@dominion.thruhere.net>,
Matt Porter <mporter@ti.com>,
linux-omap@vger.kernel.org, Kevin Hilman <khilman@ti.com>,
Paul Walmsley <paul@pwsan.com>,
devicetree-discuss@lists.ozlabs.org
Subject: Re: [RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2)
Date: Tue, 6 Nov 2012 20:45:09 +0000 [thread overview]
Message-ID: <CACxGe6sJXubOSGGg5AmDK6DQMjv60H44nax9wUnnCGsqXGbfxw@mail.gmail.com> (raw)
In-Reply-To: <A5170602-2AE7-4EC4-BE0F-0DF015A287D7@antoniou-consulting.com>
On Tue, Nov 6, 2012 at 7:34 PM, Pantelis Antoniou
<panto@antoniou-consulting.com> wrote:
> On Nov 6, 2012, at 12:14 PM, Grant Likely wrote:
>> On Tue, Nov 6, 2012 at 10:30 AM, Pantelis Antoniou
>> <panto@antoniou-consulting.com> wrote:
>>> For hot-plugging, you need it. Whether kernel code can deal with
>>> large parts of the DT going away... How about we use the dead
>>> properties method and move/tag the removed modes as such, and not
>>> really remove them.
>>
>> Nodes already use krefs, and I'm thinking about making them kobjects
>> so that they appear in sysfs and we'll have some tools to figure out
>> when reference counts don't get decremented properly.
>>
>
> From the little I've looked in the of code, and the drivers, it's going
> to be pretty bad. I don't think all users take references properly, and
> we have a big global lock for accessing the DT.
I'm a lot more optimistic on this front... I wrote a patch today to
make the change and took some measurements:
On the versatile express qemu model I measured the free memory with
/proc/device-tree, with /sys/device-tree, and with both. Here's what I
found:
/proc/device-tree only: 114776kB free
/sys/device-tree only: 114792kB free
both enabled: 114716kB free
The back of a napkin calculation indicates that on this platform
/proc/devicetree costs 76kB and /sys/device-tree costs 60kb. I'm happy
to see that using /sys instead of /proc appears to be slightly cheaper
which makes it easier to justify the change. The diffstat makes me
even happier:
arch/arm/plat-omap/Kconfig | 1 -
arch/powerpc/platforms/pseries/dlpar.c | 23 -----------
arch/powerpc/platforms/pseries/reconfig.c | 40 ------------------
drivers/of/Kconfig | 8 ----
drivers/of/base.c | 116
++++++++++++++++++++++++++++------------------------
drivers/of/fdt.c | 5 ++-
fs/proc/Makefile | 1 -
fs/proc/proc_devtree.c | 13 +-----
fs/proc/root.c | 4 +-
include/linux/of.h | 35 ++++++++++++----
include/linux/proc_fs.h | 16 --------
include/linux/string.h | 11 +++++
12 files changed, 107 insertions(+), 166 deletions(-)
There are still a few odds and ends that need to be tidied up, but
I'll get it out for review shortly. I've not touched the sparc code
yet, and I need to take another look over the existing OF_DYNAMIC
code. I think that CONFIG_OF_DYNAMIC will probably go away and the add
node/property functions will get used by fdt.c and pdt.c for initial
construction of the device tree.
> Adding and removing nodes at runtime as part of the normal operation of
> the system (and not as something that happens once in a blue moon under
> controlled conditions) will uncover lots of bugs.
I'm hoping so! Its time to clean that mess up. :-) Fortunately adding
nodes is not where we're going to have problems. The problems will be
on node removal. Addition-only at least means we can have something
useful before hunting down and squashing all the bugs.
> So let's think about locking too
Yes, the locking does need to be sorted out.
g.
next prev parent reply other threads:[~2012-11-06 20:45 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-05 20:40 [RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2) Grant Likely
2012-11-05 21:40 ` Tabi Timur-B04825
2012-11-05 23:22 ` Tony Lindgren
2012-11-09 12:06 ` Grant Likely
2012-11-06 0:07 ` Grant Likely
2012-11-06 10:31 ` Pantelis Antoniou
2012-11-07 22:35 ` Ryan Mallon
2012-11-08 13:28 ` Koen Kooi
2012-11-08 14:09 ` Timur Tabi
2012-11-08 17:00 ` Mitch Bradley
2012-11-06 10:30 ` Pantelis Antoniou
2012-11-06 11:14 ` Grant Likely
2012-11-06 18:35 ` Tony Lindgren
2012-11-06 19:29 ` Russ Dill
2012-11-06 19:41 ` Pantelis Antoniou
2012-11-06 22:17 ` Stephen Warren
2012-11-06 19:34 ` Pantelis Antoniou
2012-11-06 20:45 ` Grant Likely [this message]
2012-11-06 20:50 ` Grant Likely
2012-11-07 8:06 ` Pantelis Antoniou
2012-11-07 15:33 ` Alan Tull
2012-11-09 17:03 ` Grant Likely
2012-11-07 8:13 ` Pantelis Antoniou
2012-11-07 10:19 ` Benoit Cousson
2012-11-07 11:02 ` Pantelis Antoniou
2012-11-07 11:12 ` Benoit Cousson
2012-11-07 11:23 ` Pantelis Antoniou
2012-11-09 20:33 ` Grant Likely
2012-11-12 11:34 ` Pantelis Antoniou
2012-11-12 13:01 ` Grant Likely
2012-11-07 17:25 ` Stephen Warren
2012-11-07 22:10 ` Pantelis Antoniou
2012-11-08 10:36 ` Cousson, Benoit
2012-11-09 5:32 ` Joel A Fernandes
2012-11-09 14:29 ` David Gibson
2012-11-10 3:15 ` Joel A Fernandes
2012-11-09 21:22 ` Grant Likely
2012-11-12 11:47 ` Pantelis Antoniou
2012-11-13 3:59 ` Joel A Fernandes
2012-11-09 22:59 ` Stephen Warren
[not found] ` <-4237940489086529028@unknownmsgid>
[not found] ` <559B8433-67C3-4A1A-A5D6-859907655176@antoniou-consulting.com>
2012-11-10 3:36 ` Joel A Fernandes
2012-11-12 12:48 ` Pantelis Antoniou
2012-11-13 2:28 ` David Gibson
2012-11-06 22:37 ` Stephen Warren
2012-11-07 0:54 ` Mitch Bradley
2012-11-09 17:02 ` Grant Likely
2012-11-12 11:29 ` Pantelis Antoniou
2012-11-07 8:47 ` Pantelis Antoniou
2012-11-07 17:18 ` Stephen Warren
2012-11-07 22:08 ` Pantelis Antoniou
2012-11-09 16:28 ` Grant Likely
2012-11-09 23:23 ` Stephen Warren
2012-11-09 23:40 ` Grant Likely
2012-11-12 10:53 ` Koen Kooi
2012-11-12 12:10 ` Pantelis Antoniou
2012-11-12 16:52 ` Stephen Warren
2012-11-13 7:25 ` David Gibson
2012-11-13 8:09 ` Pantelis Antoniou
2012-11-13 12:24 ` Grant Likely
2012-11-13 13:38 ` Pantelis Antoniou
2012-11-15 4:57 ` David Gibson
2012-11-13 17:10 ` Stephen Warren
2012-11-13 23:30 ` David Gibson
2012-11-14 0:00 ` Pantelis Antoniou
2012-11-13 16:57 ` Stephen Warren
2012-11-13 18:10 ` Mitch Bradley
2012-11-13 18:29 ` Stephen Warren
2012-11-13 19:09 ` Mitch Bradley
2012-11-13 19:11 ` Pantelis Antoniou
2012-11-17 22:27 ` Jean-Christophe PLAGNIOL-VILLARD
2012-11-20 17:09 ` Grant Likely
2012-11-11 20:47 ` Rob Landley
2012-11-12 12:50 ` Pantelis Antoniou
2012-11-12 16:54 ` Stephen Warren
2012-11-12 11:23 ` Pantelis Antoniou
2012-11-12 16:49 ` Stephen Warren
2012-11-12 17:00 ` Pantelis Antoniou
2012-11-12 17:10 ` Stephen Warren
2012-11-12 17:19 ` Pantelis Antoniou
2012-11-12 17:29 ` Stephen Warren
2012-11-12 17:38 ` Pantelis Antoniou
2012-11-12 20:16 ` Russ Dill
2012-11-12 16:45 ` Stephen Warren
2012-11-09 2:26 ` David Gibson
2012-11-09 15:40 ` Pantelis Antoniou
2012-11-13 0:03 ` David Gibson
2012-11-09 21:08 ` Grant Likely
2012-11-13 0:05 ` David Gibson
2012-11-09 21:42 ` Grant Likely
2012-11-13 1:05 ` David Gibson
2012-11-13 5:22 ` Stephen Warren
2012-11-13 6:54 ` David Gibson
2012-11-09 22:57 ` Stephen Warren
2012-11-09 23:27 ` Grant Likely
2012-11-12 12:05 ` Pantelis Antoniou
2012-11-09 23:14 ` Stephen Warren
2012-11-09 23:06 ` Stephen Warren
2012-11-09 23:32 ` Grant Likely
2012-11-12 11:03 ` Koen Kooi
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