Is this comment the executive summary?
+ /* + * Large reads cause the kernel to validate more memory before + * starting the actual read, and hence cause slowdowns. + * Ideally you read as much as you're going to receive. + * This buffer calculation algorithm tries to optimise the + * read length depending on past read chunksizes. + * For network reads this allows it to follow the packetsizes. + * The initial read will attempt the full buffer. + */
Sounds ok, but only in 7.9, of course.