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SubjectRe: [patch] SLQB slab allocator
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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



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