Even when disk caches are involved (ie. data in RAM, not cache), a typical grep application (short "needle" to search for) should saturate the memory bandwidth

Even when disk caches are involved (ie. data in RAM, not cache), a typical grep application (short "needle" to search for) should saturate the memory bandwidth before CPU cores. Running a few threads/processes in parallel could improve throughput with latency hiding, but adding more shouldn't give any benefit.