Messages in this thread | | | From | Daniel Mentz <> | Date | Wed, 25 Oct 2017 10:55:08 -0700 | Subject | Re: [PATCH] genalloc: Make the avail variable an atomic64_t |
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I found that genalloc is very slow for large chunk sizes because bitmap_find_next_zero_area has to grind through that entire bitmap. Hence, I recommend avoiding genalloc for large chunk sizes.
I'm thinking how this would behave on a 32 bit ARM platform
On Wed, Oct 25, 2017 at 8:32 AM, <sbates@raithlin.com> wrote: > --- a/lib/genalloc.c > +++ b/lib/genalloc.c > @@ -194,7 +194,7 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy > chunk->phys_addr = phys; > chunk->start_addr = virt; > chunk->end_addr = virt + size - 1; > - atomic_set(&chunk->avail, size); > + atomic64_set(&chunk->avail, size);
Isn't size defined as a size_t type which is 32 bit wide on ARM? How can you ever set chunk->avail to anything larger than 2^32 - 1?
> @@ -464,7 +464,7 @@ size_t gen_pool_avail(struct gen_pool *pool) > > rcu_read_lock(); > list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) > - avail += atomic_read(&chunk->avail); > + avail += atomic64_read(&chunk->avail);
avail is defined as size_t (32 bit). Aren't you going to overflow that variable?
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