Messages in this thread | | | Date | Sat, 14 Feb 2004 11:01:08 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH] __alloc_pages - NUMA and lower zone protection |
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Martin Hicks wrote:
>Hi, > >There is a problem with the current __alloc pages on a machine with many >nodes. As we go down the zones[] list, we may move onto other nodes. >Each time we go to the next zone we protect these zones by doing >"min += local_low". > >This is quite appropriate on a machine with one node, but wrong on >machines with other nodes. To illustrate, here is an example. On a >256 node Altix machine, a request on node 0 for 2MB requires just over >600MB of free memory on the 256th node in order to fullfil the "min" >requirements if all other nodes are low on memory. This could leave >73GB of memory unallocated across all nodes. > >This patch keeps the same semantics for lower_zone_protection, but only >provides protection for higher priority zones in the same node. > >The patch seems to do the right thing on my non-NUMA zx1 ia64 machine >(which has ZONE_DMA and ZONE_NORMAL) as well as the multi-node Altix. > >
Could you add a comment or two, please?
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