Re: [Qemu-devel] virtio-scsi-pci iothread spins at 100%

[Ed Swierk]

On Wed, Feb 8, 2017 at 5:47 PM, Fam Zheng <address@hidden> wrote:
> No, something is wrong. The polling shouldn't keep running when there is no 
> I/O
> activity.
>
> Can you try "perf top" to see what poll handlers are spinning?

Samples: 288K of event 'cycles', Event count (approx.): 57149970643
Overhead  Shared Object            Symbol
  16.96%  qemu-system-x86_64       [.] lduw_le_phys
  15.77%  [vdso]                   [.] __vdso_clock_gettime
   7.25%  qemu-system-x86_64       [.] qemu_lockcnt_cmpxchg_or_wait
   7.16%  qemu-system-x86_64       [.] aio_poll
   3.94%  qemu-system-x86_64       [.] address_space_translate
   3.69%  qemu-system-x86_64       [.] qemu_lockcnt_dec
   3.46%  qemu-system-x86_64       [.] virtio_queue_host_notifier_aio_poll
   3.32%  qemu-system-x86_64       [.] address_space_translate_internal
   2.54%  qemu-system-x86_64       [.] run_poll_handlers_once
   2.54%  libpthread-2.19.so       [.] pthread_mutex_lock
   2.53%  libpthread-2.19.so       [.] __pthread_mutex_unlock_usercnt
   2.53%  qemu-system-x86_64       [.] aio_notify_accept
   2.40%  qemu-system-x86_64       [.] timerlist_deadline_ns
   2.38%  qemu-system-x86_64       [.] address_space_lookup_region
   2.23%  qemu-system-x86_64       [.] timerlistgroup_deadline_ns
   2.21%  qemu-system-x86_64       [.] qemu_lockcnt_inc
   2.08%  qemu-system-x86_64       [.] qemu_clock_get_ns
   1.91%  qemu-system-x86_64       [.] object_dynamic_cast_assert
   1.54%  qemu-system-x86_64       [.] virtio_queue_notify_aio_vq.part.16
   1.21%  qemu-system-x86_64       [.] qemu_map_ram_ptr
   1.16%  libc-2.19.so             [.] __clock_gettime
   1.02%  qemu-system-x86_64       [.] event_notifier_poll
   1.02%  qemu-system-x86_64       [.] timerlistgroup_run_timers
   1.02%  qemu-system-x86_64       [.] virtio_queue_set_notification
   0.82%  qemu-system-x86_64       [.] aio_bh_poll
   0.81%  qemu-system-x86_64       [.] timerlist_run_timers
   0.70%  qemu-system-x86_64       [.] aio_dispatch
   0.66%  qemu-system-x86_64       [.] virtio_queue_empty.part.32
   0.62%  qemu-system-x86_64       [.] aio_compute_timeout
   0.50%  qemu-system-x86_64       [.] virtio_scsi_data_plane_handle_event
   0.32%  qemu-system-x86_64       [.] address@hidden
   0.26%  qemu-system-x86_64       [.] memory_region_is_ram_device
   0.21%  qemu-system-x86_64       [.] qemu_mutex_unlock
   0.12%  qemu-system-x86_64       [.] aio_context_acquire
   0.12%  qemu-system-x86_64       [.] iothread_run
   0.12%  qemu-system-x86_64       [.] qemu_lockcnt_count
   0.11%  qemu-system-x86_64       [.] address@hidden
   0.11%  qemu-system-x86_64       [.] qemu_mutex_lock
   0.11%  [kernel]                 [k] vmx_vcpu_run
   0.10%  libpthread-2.19.so       [.] pthread_mutex_unlock
   0.09%  qemu-system-x86_64       [.] aio_context_release
   0.09%  qemu-system-x86_64       [.] address@hidden
   0.09%  [kernel]                 [k] native_write_msr_safe
   0.08%  [kernel]                 [k] ksm_do_scan
   0.07%  qemu-system-x86_64       [.] virtio_scsi_handle_event_vq

--Ed