rt61pci issue

[Tim Blechmann <tim@klingt.org>]

hi all,

i am using tn rt61pci driver and besides having not the best wireless 
performance, it network transfer sometimes disturbs the audio playback on my 
machine. sometimes it works fine, but the machine can get into a state, where i 
will have to reboot the machine to get back to normal. i suppose, this is 
because of the rt61pci driver.

in general if found, that the specific irq thread produces a lot of interrupts 
and does quite a lot of work. the specific irq thread takes quite some cpu time 
(currently i have an uptime of 5 hours and the irq thread used 4 minutes of cpu 
time) and about 200 interupts are issued per second:

cat /proc/interrupts |grep 16\: && sleep 1 && cat /proc/interrupts | grep 16\:
  16:          0    5140126          0          0   IO-APIC-fasteoi   
uhci_hcd:usb3, ahci, 0000:08:00.0
  16:          0    5140357          0          0   IO-APIC-fasteoi   
uhci_hcd:usb3, ahci, 0000:08:00.0

using perf, i get the following data about the spent cpu time:
# Events: 106  cycles
#
# Overhead          Command      Shared Object  Symbol
# ........  ...............  .................  ......
#
    61.17%  irq/16-0000:08:  [rt61pci]          [k] rt61pci_interrupt_thread
    12.77%  irq/16-0000:08:  [rt61pci]          [k] rt61pci_set_device_state
     3.72%  irq/16-0000:08:  [kernel.kallsyms]  [k] __ticket_spin_lock
     3.17%  irq/16-0000:08:  [kernel.kallsyms]  [k] local_bh_disable
     2.14%  irq/16-0000:08:  [kernel.kallsyms]  [k] schedule
     1.81%  irq/16-0000:08:  [rt61pci]          [k] rt61pci_kick_tx_queue
     1.50%  irq/16-0000:08:  [mac80211]         [k] prepare_for_handlers
     1.38%  irq/16-0000:08:  [rt2x00pci]        [k] rt2x00pci_rxdone
     1.03%  irq/16-0000:08:  [kernel.kallsyms]  [k] __ticket_spin_unlock
     0.87%  irq/16-0000:08:  [kernel.kallsyms]  [k] __inet_lookup_established
     0.87%  irq/16-0000:08:  [kernel.kallsyms]  [k] tcp_event_data_recv
     0.82%  irq/16-0000:08:  [kernel.kallsyms]  [k] irq_thread
     0.66%  irq/16-0000:08:  [kernel.kallsyms]  [k] update_curr_rt
     0.64%  irq/16-0000:08:  [rt2x00lib]        [k] rt2x00lib_rxdone
     0.64%  irq/16-0000:08:  [kernel.kallsyms]  [k] mod_timer
     0.51%  irq/16-0000:08:  [kernel.kallsyms]  [k] pick_next_task_rt
     0.51%  irq/16-0000:08:  [kernel.kallsyms]  [k] cpupri_set
     0.51%  irq/16-0000:08:  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore
     0.50%  irq/16-0000:08:  [kernel.kallsyms]  [k] hrtick_update
     0.49%  irq/16-0000:08:  [kernel.kallsyms]  [k] __phys_addr
     0.49%  irq/16-0000:08:  [kernel.kallsyms]  [k] update_shares
     0.49%  irq/16-0000:08:  [kernel.kallsyms]  [k] dequeue_task
     0.49%  irq/16-0000:08:  [kernel.kallsyms]  [k] dequeue_rt_stack
     0.49%  irq/16-0000:08:  [kernel.kallsyms]  [k] skb_release_data
     0.44%  irq/16-0000:08:  [kernel.kallsyms]  [k] load_balance
     0.40%  irq/16-0000:08:  [kernel.kallsyms]  [k] memcpy
     0.36%  irq/16-0000:08:  [kernel.kallsyms]  [k] map_single
     0.36%  irq/16-0000:08:  [kernel.kallsyms]  [k] ip_output
     0.36%  irq/16-0000:08:  [kernel.kallsyms]  [k] tcp_ack
     0.22%  irq/16-0000:08:  [mac80211]         [k] minstrel_ht_tx_status
     0.22%  irq/16-0000:08:  [kernel.kallsyms]  [k] tcp_v4_rcv
     0.00%  irq/16-0000:08:  [kernel.kallsyms]  [k] native_write_msr_safe

not sure, if this is really helpful, but this amount of interrupts doesn't look 
good to me. if i can be on any further help to track down this issue, i would be 
happy to assist.

thanks, tim

-- 
tim@klingt.org
http://tim.klingt.org

Life is really simple, but we insist on making it complicated.
  Confucius