Re: [POLL] SLAB : Are the 32 and 192 bytes caches really usefull on x86_64 machines ?

Jörn Engel
2006-01-02T15:47:04Z

On Mon, 2 January 2006 14:56:22 +0100, Andi Kleen wrote:
>
> I wasn't proposing fully dynamic slabs, just a better default set
> of slabs based on real measurements instead of handwaving (like
> the power of two slabs seemed to have been generated). With separate
> sets for 32bit and 64bit.
>
> Also the goal wouldn't be better performance, but just less waste of memory.

My fear would be that this leads to something like the gperf: a
perfect distribution of slab caches - until any tiny detail changes.
But maybe there is a different distribution that is "pretty good" for
all configurations and better than powers of two.

> I suspect such a move could save much more memory on small systems
> than any of these "make fundamental debugging tools a CONFIG" patches ever.

Unlikely. SLOB should be better than SLAB for those purposes, no
matter how you arrange the slab caches.

Jörn

--
Fancy algorithms are slow when n is small, and n is usually small.
Fancy algorithms have big constants. Until you know that n is
frequently going to be big, don't get fancy.
-- Rob Pike