On Tue, Feb 13, 2018 at 7:00 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: > Hi Rob, > > On 02/11/18 22:56, Frank Rowand wrote: >> Hi Rob, >> >> On 02/11/18 22:27, 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() if modules are not >>> enabled. >>> >>> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx> >>> --- >>> >>> Changes since v1: >>> - change short description from >>> of: cache phandle nodes to reduce cost of of_find_node_by_phandle() >>> - rebase on v4.16-rc1 >>> - reorder new functions in base.c to avoid forward declaration >>> - add locking around kfree(phandle_cache) for memory ordering >>> - add explicit check for non-null of phandle_cache in >>> of_find_node_by_phandle(). There is already a check for !handle, >>> which prevents accessing a null phandle_cache, but that dependency >>> is not obvious, so this check makes it more apparent. >>> - do not free phandle_cache if modules are enabled, so that >>> cached phandles will be available when modules are loaded >> >> < snip > >> >> >> >> In a previous thread, you said: >> >>> 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. >> >> And I replied: >> >> Thanks for pointing out that kfree() can be used for memory alloced >> with memblock. I'll change to populate the cache earlier. >> >> >> I started to make this change when I moved forward to v4.16-rc1. There >> are two obvious ways to do this. > > < snip > > > And I did not finish the explanation, sorry. I meant to finish with saying > that given the drawbacks that I ended up not making the change for v2. > > While modifying the patch to respond to the v2 comments, I decided to go > ahead and try using memblock to alloc memory earlier. The result I got > was that when I tried to kfree() the memory at late_initcall_sync I got > a panic. The alloc function I used is memblock_virt_alloc(). You mention > "slab" specifically. Maybe the problem is that my system is using "slub" > instead. Dunno... Maybe memblock_free() still works? Or there's something else that needs to be done to transfer them. In any case, I guess doing it later is fine. And by slab, I mean the allocator, not the implementation (which can be slab, slub, or slob). Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
