On 01/31/18 12:05, frowand.l...@gmail.com wrote: > From: Frank Rowand <frank.row...@sony.com> > > Create a cache of the nodes that contain a phandle property. Use this > cache to find the node for a given phandle value instead of scanning > the devicetree to find the node. If the phandle value is not found > in the cache, of_find_node_by_phandle() will fall back to the tree > scan algorithm. > > The cache is initialized in of_core_init(). > > The cache is freed via a late_initcall_sync(). > > Signed-off-by: Frank Rowand <frank.row...@sony.com> > --- > > Some of_find_by_phandle() calls may occur before the cache is > initialized or after it is freed. For example, for the qualcomm > qcom-apq8074-dragonboard, 11 calls occur before the initialization > and 80 occur after the cache is freed (out of 516 total calls.) > > > drivers/of/base.c | 85 > ++++++++++++++++++++++++++++++++++++++++++++++--- > drivers/of/of_private.h | 5 +++ > drivers/of/resolver.c | 21 ------------ > 3 files changed, 86 insertions(+), 25 deletions(-)
Some observations.... The size of the cache for a normal device tree would be a couple of words of overhead for the cache, plus one pointer per devicetree node that contains a phandle property. This will be less space than would be used by adding a hash field to each device node. It is also less space than was used by the older algorithm (long gone) that added a linked list through the nodes that contained a phandle property. This is assuming that the values of the phandle properties are the default ones created by the dtc compiler. In the case where a very large phandle property value is hand-coded in a devicetree source, the size of the cache is capped at one entry per node. In this case, a little bit of space will be wasted -- but this is just a sanity fallback, it should not be encountered, and can be fixed by fixing the devicetree source.
