[tbr1]

DDIO operates mostly transparently to software, with the I/O controller feeding DMAs into a slice of L3. Hardware can opt out by setting PCIe TLP header hints, and you have some system-wide configurability via MSRs, but it's not something a userspace application can take into its own hands.

[b20000]

so is this taken advantage of by the OnLoad drivers of solarflare cards, for example?

[isogon]

Noticed this just now. It is.