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

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Message-ID: <nycvar.YSQ.7.76.1710061902240.1834@knanqh.ubzr>
Date:   Fri, 6 Oct 2017 19:24:42 -0400 (EDT)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Rob Herring <robh@...nel.org>
cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Grant Likely <glikely@...retlab.ca>
Subject: Re: [PATCH 0/6] Shrinking DT memory usage

On Fri, 6 Oct 2017, Rob Herring wrote:

> On Fri, Oct 6, 2017 at 4:30 PM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> > On Thu, 5 Oct 2017, 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.
> >
> > My test case went from 118072 bytes ddown to 21548 bytes with this
> > series.
> 
> Did that include the changes for FDT skipping status=disabled and to
> stop storing the full path of every node? With those 2 alone you said
> it dropped to 25K.

No -- that's with those 6 patches only.

Adding the other 2 patches on top and it is down to 11732 bytes.


Nicolas