mir_proving_server with INTEL_DEBUG=perf says: CPU mapping a busy miptree BO stalled and took 0.078 ms.

mir_proving_server with INTEL_DEBUG=perf says this when some clients (hardware or software) run:

CPU mapping a busy miptree BO stalled and took 0.078 ms.
CPU mapping a busy miptree BO stalled and took 0.038 ms.
CPU mapping a busy miptree BO stalled and took 0.005 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.000 ms.
CPU mapping a busy miptree BO stalled and took 0.000 ms.
CPU mapping a busy miptree BO stalled and took 0.000 ms.
CPU mapping a busy miptree BO stalled and took 0.000 ms.
CPU mapping a busy miptree BO stalled and took 0.080 ms.
CPU mapping a busy miptree BO stalled and took 0.128 ms.
CPU mapping a busy miptree BO stalled and took 0.005 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.004 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.004 ms.
CPU mapping a busy miptree BO stalled and took 0.146 ms.
CPU mapping a busy miptree BO stalled and took 0.089 ms.
CPU mapping a busy miptree BO stalled and took 0.008 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.002 ms.
CPU mapping a busy miptree BO stalled and took 0.001 ms.
CPU mapping a busy miptree BO stalled and took 0.001 ms.
CPU mapping a busy miptree BO stalled and took 0.001 ms.
CPU mapping a busy miptree BO stalled and took 0.000 ms.
CPU mapping a busy miptree BO stalled and took 0.001 ms.