* Pekka Enberg <[EMAIL PROTECTED]> wrote: > I mostly live in the legacy 32-bit UMA/UP land still so I cannot > verify this myself but the kind folks at SGI claim the following > (again from the announcement): > > "On our systems with 1k nodes / processors we have several gigabytes > just tied up for storing references to objects for those queues This > does not include the objects that could be on those queues. One fears > that the whole memory of the machine could one day be consumed by > those queues."
Yes, you can find gigs tied up on systems that have 100 GB of RAM, or you can have gigs tied up if you over-size your caches. I'd like to see an accurate calculation done on this. > The problem is that for each cache, you have an "per-node alien > queues" for each node (see struct kmem_cache nodelists -> struct > kmem_list3 alien). Moving slab metadata to struct page solves this but > now you can only have one "queue" thats part of the same struct. yes, it's what i referred to as "distributed, per node cache". It has no "quadratic overhead". It has SLAB memory spread out amongst nodes. I.e. 1 million pages are distributed amongst 1k nodes with 1000 pages per node with each node having 1 page. But that memory is not lost and it's disingenous to call it 'overhead' and it very much comes handy for performance _IF_ there's global workload that involves cross-node allocations. It's simply a cache that is mis-sized and mis-constructed on large node count systems but i bet it makes quite a performance difference on low-node-count systems. On high node-count systems it might make sense to reduce the amount of cross-node caching and to _structure_ the distributed NUMA SLAB cache in an intelligent way (perhaps along cpuset boundaries) - but a total, design level _elimination_ of this caching concept, using very misleading arguments, just looks stupid to me ... Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/