It will show up like CPU usage - the hyperthread that is waiting for memory will appear busy executing.<p>perf can record hardware counter events - use &quot;perf list&quot; to see the list - including those that count frontend and backend stalls (stalls in the instruction decoding and execution stages respectively).  A high stall ratio &#x2F; low instructions per cycle throughput is an indicator that you&#x27;re running into memory bandwidth limitations.