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Date: Sat, 6 Feb 2010 01:53:00 -0800 (PST) From: David Rientjes <rientjes@...gle.com> To: Andi Kleen <andi@...stfloor.org> cc: submit@...stfloor.org, linux-kernel@...r.kernel.org, haicheng.li@...el.com, Pekka Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org Subject: Re: [PATCH] [1/4] SLAB: Handle node-not-up case in fallback_alloc() On Sat, 6 Feb 2010, Andi Kleen wrote: > > That other node must be allowed by current's cpuset, otherwise > > kmem_getpages() will fail when get_page_from_freelist() iterates only over > > unallowed nodes. > > All theses cases are really only interesting in the memory hotplug path > itself (afterwards the slab is working anyways and memory is there) > and if someone sets funny cpusets for those he gets what he deserves ... > If a hot-added node has not been initialized for the cache, your code is picking an existing one in zonelist order which may be excluded by current's cpuset. Thus, your code has a very real chance of having kmem_getpages() return NULL because get_page_from_freelist() will reject non-atomic ALLOC_CPUSET allocations for prohibited nodes. That isn't a scenario that requires a "funny cpuset," it just has to not allow whatever initialized node comes first in the zonelist. My suggested alternative does not pick a single initialized node, rather it tries all nodes that actually have a chance of having kmem_getpages() succeed which increases the probability that your patch actually has an effect for cpuset users. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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