Re: [PATCH] of: cache phandle nodes to decrease cost of of_find_node_by_phandle()

[Frank Rowand]

On 02/01/18 06:34, Rob Herring wrote:
> On Wed, Jan 31, 2018 at 2:05 PM,  <frowand.list@xxxxxxxxx> wrote:
>> From: Frank Rowand <frank.rowand@xxxxxxxx>
>>
>> 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.rowand@xxxxxxxx>
>> ---
>>
>> 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.)
> 
> We should be able to do this earlier. We already walk the tree twice
> in unflattening. We can get the max phandle (or number of phandles
> IMO) on the first pass, allocate with the early allocator and then
> populate the cache in the 2nd pass. AIUI, you can alloc with memblock
> and then free with kfree as the memblock allocations get transferred
> to the slab.

Thanks for pointing out that kfree() can be used for memory alloced
with memblock.  I'll change to populate the cache earlier.