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Equation 13 · Part 11 · Serving a Frontier Model: The KV Cache, Batching, and What a Token Actually Costs

Denominator: M_kv(s)

bmax⁡≈Mdevice−MweightsMkv(s),b_{\max} \approx \frac{M_{\mathrm{device}} - M_{\mathrm{weights}}}{M_{\mathrm{kv}}(s)} ,
Mkv(s)M_{\mathrm{kv}}(s)

What this part means

The complete quantity below the fraction bar; it must be nonzero for this division.

Its job in the formula

MkM_kv(s) occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

The passage around this formula

What binds is memory, and specifically the cache. Weights are shared across the batch; the key–value cache is not. Each concurrent request carries its own, and each grows with every token it generates. Achievable batch size is therefore bmax⁡≈Mdevice−MweightsMkv(s)b_{\max} \approx \frac{M_{\mathrm{device}} - M_{\mathrm{weights}}}{M_{\mathrm{kv}}(s)} . which falls as contexts lengthen. This is the mechanism behind an effect users notice without explanation: long-context workloads cost disproportionately more, because they crowd out the concurrency that made short-context serving cheap.

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Learn the underlying idea

A fraction a/b means a divided by b. The top number is the numerator; the bottom number is the denominator, and it cannot be zero.

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Sources cited in the article section

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