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SubjectRe: x86_64: Make sparsemem/vmemmap the default memory model
On Nov 12, 2007 7:42 PM, Christoph Lameter <clameter@sgi.com> wrote:
> Ok here is the patch to remove DISCONTIG and FLATMEM
>
> x86_64: Make sparsemem/vmemmap the default memory model
>
> Use sparsemem as the only memory model for UP, SMP and NUMA.
> Measurements indicate that DISCONTIGMEM has a higher overhead
> than sparsemem. And FLATMEMs benefits are minimal. So I think its
> best to simply standardize on sparsemem.
>
> Results of page allocator tests (test can be had via git from slab git
> tree branch tests)
>
> Measurements in cycle counts. 1000 allocations were performed and then the
> average cycle count was calculated.
>
> Order FlatMem Discontig SparseMem
> 0 639 665 641
> 1 567 647 593
> 2 679 774 692
> 3 763 967 781
> 4 961 1501 962
> 5 1356 2344 1392
> 6 2224 3982 2336
> 7 4869 7225 5074
> 8 12500 14048 12732
> 9 27926 28223 28165
> 10 58578 58714 58682

Discontig obviously needs to die. However, FlatMem is consistently
faster, averaging about 2.1% better overall for your numbers above. Is
the page allocator not, erm, a fast path, where that matters?

Order Flat Sparse % diff
0 639 641 0.3
1 567 593 4.4
2 679 692 1.9
3 763 781 2.3
4 961 962 0.1
5 1356 1392 2.6
6 2224 2336 4.8
7 4869 5074 4.0
8 12500 12732 1.8
9 27926 28165 0.8
10 58578 58682 0.2
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