Re: [RFC][PATCH 2/2] Explicitly retry hugepage allocations

[Christoph Lameter <clameter@sgi.com>]

On Wed, 6 Feb 2008, Nishanth Aravamudan wrote:

> Add __GFP_REPEAT to hugepage allocations. Do so to not necessitate
> userspace putting pressure on the VM by repeated echo's into
> /proc/sys/vm/nr_hugepages to grow the pool. With the previous patch to
> allow for large-order __GFP_REPEAT attempts to loop for a bit (as
> opposed to indefinitely), this increases the likelihood of getting
> hugepages when the system experiences (or recently experienced) load.
> 
> On a 2-way x86_64, this doubles the number of hugepages (from 10 to 20)
> obtained while compiling a kernel at the same time. On a 4-way ppc64,
> a similar scale increase is seen (from 3 to 5 hugepages). Finally, on a
> 2-way x86, this leads to a 5-fold increase in the hugepages allocatable
> under load (90 to 554).

Hmmm... How about defaulting to __GFP_REPEAT by default for larger page 
allocations? There are other users of larger allocs that would also 
benefit from the same measure. I think it would be fine as long as we are 
sure to fail at some point.

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