Re: [PATCH] __alloc_pages - NUMA and lower zone protection

[Nick Piggin]

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?

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/