Messages in this thread |  | | Date | Fri, 13 Feb 2015 13:20:10 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH 1/3] Slab infrastructure for array operations |
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On Fri, 13 Feb 2015, Christoph Lameter wrote:
> > I also think that this implementation is slub-specific. For example, > > in slab case, it is always better to access local cpu cache first than > > page allocator since slab doesn't use list to manage free objects and > > there is no cache line overhead like as slub. I think that, > > in kmem_cache_alloc_array(), just call to allocator-defined > > __kmem_cache_alloc_array() is better approach. > > What do you mean by "better"? Please be specific as to where you would see > a difference. And slab definititely manages free objects although > differently than slub. SLAB manages per cpu (local) objects, per node > partial lists etc. Same as SLUB. The cache line overhead is there but no > that big a difference in terms of choosing objects to get first. >
I think because we currently lack a non-fallback implementation for slab that it may be premature to discuss what would be unified if such an implementation were to exist. That unification can always happen later if/when the slab implementation is proposed, but I don't think we should be unifying an implementation that doesn't exist.
In other words, I think it would be much cleaner to do just define the generic array alloc and array free functions in mm/slab_common.c along with their EXPORT_SYMBOL()'s as simple callbacks to per-allocator __kmem_cache_{alloc,free}_array() implementations. I think it's also better from a source code perspective to avoid reading two different functions and then realizing that nothing is actually unified between them (and the absence of an unnecessary #ifdef is currently helpful).
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