linux-kernel - Re: [PATCH 0/6] Shrinking DT memory usage

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Date:   Fri, 6 Oct 2017 19:11:37 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     Nicolas Pitre <nico@...aro.org>,
        Grant Likely <glikely@...retlab.ca>
Subject: Re: [PATCH 0/6] Shrinking DT memory usage

On 10/05/17 12:44, Rob Herring wrote:
> On kernels with a minimal config and a RAM target in the 100s of KB, DT 
> is quite a hog of runtime memory usage. How much is dependent on how many
> nodes and properties in the DT which have a corresponding struct device_node
> and struct property in the kernel. Just skipping disabled nodes saves a 
> lot by not creating the device_nodes in the first place[1], but there's 
> more low hanging fruit by making some of the fields in struct property and
> struct device_node optional. With the changes here, the memory usage goes
> from 17KB to under 8KB on QEMU's ARM virt machine which is a relatively 
> small DT.
> 
> The majority of the diffstat here is just moving all the kobject/sysfs 
> related code to its own file so we can avoid adding a bunch of ifdefs.
> 
> There's more drastic approaches we could take such as doing the 
> unflattening at build time and storing the bulk of the unflattened tree 
> as const data. Grant also has some ideas on storing properties as ids 
> instead. He's explained it to me, but I still don't understand it.
> 
> Rob
> 
> [1] https://patchwork.kernel.org/patch/9983203/
> 
> Rob Herring (6):
>   of: fix missing kobject init for !SYSFS && OF_DYNAMIC config
>   of: remove struct property.unique_id for FDT
>   of: make struct property _flags field configurable
>   of: move kobj_to_device_node() into dynamic.c
>   of: wrap accesses to device_node kobject
>   of: make kobject and bin_attribute support configurable
> 
>  drivers/base/core.c     |   2 +-
>  drivers/of/Kconfig      |   4 ++
>  drivers/of/Makefile     |   1 +
>  drivers/of/base.c       | 133 ---------------------------------------
>  drivers/of/dynamic.c    |  27 ++------
>  drivers/of/kobj.c       | 164 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/of_private.h |  29 +++++++--
>  include/linux/of.h      |  28 +++++----
>  8 files changed, 215 insertions(+), 173 deletions(-)
>  create mode 100644 drivers/of/kobj.c
> 

For the entire series:

Reviewed-by: Frank Rowand <frowand.list@...il.com>

I don't know if there will be any conflicts between my series
"[PATCH 00/12] of: overlay: clean up device tree overlay code"
and this series.

If you choose to apply this series first, I will make any needed
changes to my series.

-Frank