A system, method and article of manufacture for reducing latencies
associated with cache coherence directory misses on external caches in a
shared distributed memory data processing system. A cache coherence
directory is evaluated for possible prefetching of a directory entry into
a directory cache. A prefetch miss indicator is set if the prefetch
evaluation results in a directory miss. The prefetch miss indicator is
consulted during subsequent processing of a memory block request
corresponding to the directory entry. An accelerated snoop response
action is taken if the prefetch miss indicator is set. The latency of a
second lookup into the cache coherence directory, which would otherwise
be required, is thereby avoided.