Model

When a cache entry pays

P/S is a natural batch size, with reuse count as the batch.

R = \frac{λ}{w _{eff}} > \frac{P}{S}, w_{eff} = i \sum w_{i}

$λ$: Read rate; the rate of reads on the object
$w$: Write rate; the rate of writes that invalidate it; summed over its dependencies
$P$: Cost to produce; the cost of computing one version
$S$: Saving; what serving one read from the cache saves
$R$: Reuse factor; reads per version

How it behaves

One input on the horizontal axis, the others held fixed.

Data table

Every number the mechanisms quote for this relationship is recomputed from it, so none of them disagrees with it.

Each mechanism states it in its own names. The general symbol each name stands for is shown with it.

Caching
What happens when we deliberately keep a second copy of data that no protocol forces to be correct?
$R = λ / w > P / S$
Read it in place →
Caching
What happens when we deliberately keep a second copy of data that no protocol forces to be correct?
$λ / w > P / S$
Read it in place →