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SubjectRe: [patch 2/2] slub: add min_partial sysfs tunable
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Hi David,

On Mon, 23 Feb 2009, Pekka Enberg wrote:
> > The patches look good but the description is bit lacking. Does this
> > actually fix up something? Why don't we fix the limit calculations
> > instead?
> >
> > I'm a sucker for numbers so I'm easily fooled into merging patches with
> > statements of the form "this shaves off N bytes/kb/mb on XYZ systems".

On Mon, 2009-02-23 at 01:58 -0800, David Rientjes wrote:
> The memory savings from simply moving min_partial from struct
> kmem_cache_node to struct kmem_cache is obviously not significant (unless
> maybe you're from SGI or something), at the largest it's
>
> # allocated caches * (MAX_NUMNODES - 1) * sizeof(unsigned long)
>
> The true savings occurs when userspace reduces the number of partial slabs
> that would otherwise be wasted, especially on machines with a large
> number of nodes (ia64 with CONFIG_NODES_SHIFT at 10 for default?). As
> well as the kernel estimates ideal values for n->min_partial and ensures
> it's within a sane range, userspace has no other input other than writing
> to /sys/kernel/slab/cache/shrink.

Applied with the above explanation added to the changelog. Thanks!

Pekka



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