Event items are used for completing Surface Aggregator EC events, i.e. placing event command data and payload on a workqueue for later processing to avoid doing said processing directly on the receiver thread. This means that event items are allocated for each incoming event, regardless of that event being transmitted via sequenced or unsequenced packets. On the Surface Book 3 and Surface Laptop 3, touchpad HID input events (unsequenced), can constitute a larger amount of traffic, and therefore allocation of event items. This warrants caching event items to reduce memory fragmentation. The size of the cached objects is specifically tuned to accommodate keyboard and touchpad input events and their payloads on those devices. As a result, this effectively also covers most other event types. In case of a larger event payload, event item allocation will fall back to kzalloc(). Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Link: https://lore.kernel.org/r/20201221183959.1186143-4-luzmaximilian@gmail.com Signed-off-by: Hans de Goede <hdegoede@redhat.com>