Re: [patch] SLQB slab allocator

[Pekka Enberg]

Hi Andi,

On Fri, 2009-01-23 at 10:55 +0100, Andi Kleen wrote:
> > +#if L1_CACHE_BYTES < 64
> > +	if (size > 64 && size <= 96)
> > +		return 1;
> > +#endif
> > +#if L1_CACHE_BYTES < 128
> > +	if (size > 128 && size <= 192)
> > +		return 2;
> > +#endif
> > +	if (size <=	  8) return 3;
> > +	if (size <=	 16) return 4;
> > +	if (size <=	 32) return 5;
> > +	if (size <=	 64) return 6;
> > +	if (size <=	128) return 7;
> > +	if (size <=	256) return 8;
> > +	if (size <=	512) return 9;
> > +	if (size <=       1024) return 10;
> > +	if (size <=   2 * 1024) return 11;
> > +	if (size <=   4 * 1024) return 12;
> > +	if (size <=   8 * 1024) return 13;
> > +	if (size <=  16 * 1024) return 14;
> > +	if (size <=  32 * 1024) return 15;
> > +	if (size <=  64 * 1024) return 16;
> > +	if (size <= 128 * 1024) return 17;
> > +	if (size <= 256 * 1024) return 18;
> > +	if (size <= 512 * 1024) return 19;
> > +	if (size <= 1024 * 1024) return 20;
> > +	if (size <=  2 * 1024 * 1024) return 21;
> 
> Have you looked into other binsizes?  iirc the original slab paper
> mentioned that power of two is usually not the best.

Judging by the limited boot-time testing I've done with kmemtrace, the
bulk of kmalloc() allocations are under 64 bytes or so and actually a
pretty ok fit with the current sizes. The badly fitting objects are
usually very big and of different sizes (so they won't share a cache
easily) so I'm not expecting big gains from non-power of two sizes.

			Pekka

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/