Channel Delays due to CPU Cache Back Ups
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
In certain systems data currently resident in a CPU cache buffer is not transferred into main storage until the storage controls execute a page "cast-out" operation. If an I/O channel issues a fetch request to main storage for data which is currently resident in such a cache buffer, e.g., for a CCW (Channel Command Word), the request is placed in a queue, pending later completion of an associated cast-out operation. The storage controls must later re-issue the request. Since the period for completion of such cast-out operation is necessarily of indefinite duration, the channel is susceptible of experiencing operational overrun during this period (with resulting degradation of channel and system performance).