Re: slub: slab order on multi-processor machines

From: Roman Gushchin
Date: Fri Jun 07 2013 - 13:09:43 EST

On 07.06.2013 18:12, Christoph Lameter wrote:
On Fri, 7 Jun 2013, Roman Gushchin wrote:

As I understand, the idea was to make kernel allocations cheaper by reducing
the total
number of page allocations (allocating 1 page with order 3 is cheaper than
8 1-ordered pages).

Its also affecting allocator speed. By having less page structures to
manage the metadata effort is reduced. By having more objects in a page
the fastpath of slub is more likely to be used (Visible in allocator
benchmarks). Slub can fall back dynamically to order 0 pages if necessary.
So it can take opportunistically take advantage of contiguous pages.

Thank you for clarification!

May be it's reasonable to fall back to order 0 pages if it's not possible
to allocate new large page without direct compaction?
I'll try to perform some tests here.

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