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| - | ==== T02. [20p] Mpstat ==== | ||
| - | Open {{:ep:labs:fact_rcrs.zip|fact_rcrs.zip}} and look at the code. | ||
| - | |||
| - | === [10p] Task A - Python recursion depth === | ||
| - | Try to run the script while passing 1000 as a command line argument. Why does it crash? | ||
| - | |||
| - | Luckily, python allows you to both retrieve the current recursion limit //and// set a new value for it. Increase the recursion limit so that the process will never crash, regardless of input (assume that it still has a reasonable upper bound). | ||
| - | |||
| - | |||
| - | === [10p] Task B - CPU affinity === | ||
| - | Run the script again, this time passing 10000. Use **mpstat** to monitor the load on each //individual// CPU at 1s intervals. The one with close to 100% load will be the one running our script. Note that the process might be passed around from one core to another. | ||
| - | |||
| - | Stop the process. Use **stress** to create N-1 CPU workers, where N is the number of cores on your system. Use **taskset** to set the CPU affinity of the N-1 workers and then run the script again. You should notice that the process is scheduled on cpu0. | ||
| - | |||
| - | <solution -hidden> | ||
| - | **Task A:** | ||
| - | <code python> | ||
| - | import sys | ||
| - | |||
| - | N = int(sys.argv[1]) | ||
| - | |||
| - | sys.getrecursionlimit() | ||
| - | sys.setrecursionlimit(N) | ||
| - | </code> | ||
| - | |||
| - | **Task B:** | ||
| - | |||
| - | Start N-1 worker threads on cpu[1] - cpu[N-1]. Leave cpu[0] unused for when we run the script. | ||
| - | |||
| - | <code bash> | ||
| - | $ taskset 0xfe stress -c $(( $(nproc) - 1 )) | ||
| - | </code> | ||
| - | </solution> | ||
