Re: [PATCH] arm64: Increase the max granular size

From: Christoph Lameter
Date: Tue Nov 03 2015 - 18:33:33 EST

On Tue, 3 Nov 2015, Catalin Marinas wrote:

> (cc'ing Jonsoo and Christoph; summary: slab failure with L1_CACHE_BYTES
> of 128 and sizeof(kmem_cache_node) of 152)

Hmmm... Yes that would mean use the 196 sized kmalloc array which is not a
power of two slab. But the code looks fine to me.

> If I revert commit 8fc9cf420b36 ("slab: make more slab management
> structure off the slab") it works but I still need to figure out how
> slab indices are calculated. The size_index[] array is overridden so
> that 0..15 are 7 and 16..23 are 8. But the kmalloc_caches[7] has never
> been populated, hence the BUG_ON. Another option may be to change
> kmalloc_size and kmalloc_index to cope with KMALLOC_MIN_SIZE of 128.
> I'll do some more investigation tomorrow.

The commit allows off slab management for PAGE_SIZE >> 5 that is 128.

After that commit kmem_cache_create would try to allocate an off slab
management structure which is not available during early boot.
But the slab_early_init is set which should prevent the use of an off slab
management infrastructure in kmem_cache_create().

However, the failure in line 2283 shows that the OFF SLAB flag was
mistakenly set anyways!!!! Something must havee cleared slab_early_init?

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