Hi,
I have a latency issue using the linux-2.6.33.7-rt29 kernel.
Here is my setup :
| Board 1| | Board 2|
PC --> --> eth->wifi->wifi->eth --> --> PC
|_ tap ----------DAG------- tap_|
The measure is done thanks to external TAP devices.
The DAG card is on another PC and does the measure.
But it is an "out of the box" measure and this is done only after I
stop the capture by merging pcap files and using timestamps.
The issue, now...
As you can see on the following two pictures, at least two events
occur during my test.
http://rostedt.homelinux.com/rt-jitter/latencies_1500us_rt_cable_noip7.png
http://rostedt.homelinux.com/rt-jitter/latencies_1500us_rt_cable_noip8.png
Each graph is representing the latency in Âs vs. the packet number.
Each packet is separated from the previous one by 1500Âs.
I don't have any IP address configured (I removed the loopback and all
other interfaces are configured using ifconfig 0.0.0.0).
The problem occurs in PREEMPT_RT and PREEMPT_DESKTOP.
The period is bigger when I change HZ (I am currently using HZ=1000).
Hrtimers are configured, but even when not using it, the problem is the same.
I have done many many tests, removing timers, changing frequencies, etc.
I also tried to change priority of my processes associated with
sirq-rx, sirq-tx, and the interrupts.
I can't find the cause.
If you have *any* idea, thanks in advance !
Here are the timers after the test associated to the picture named
"latencies_1500us_rt_cable_noip8.png" :
Board 1 (eth -> wifi) :
-----------------------
Sample period: 1654.752 s
1654753, 4 sirq-timer/0 hrtimer_start_range_ns (tick_sched_timer)
1655, 4 sirq-timer/0 __enqueue_rt_entity (sched_rt_period_timer)
1649, 15 events/0 phy_state_machine (delayed_work_timer_fn)
1650, 15 events/0 msleep (process_timeout)
824, 15 events/0 msleep (process_timeout)
275, 4 sirq-timer/0 arm_supers_timer (sync_supers_timer_fn)
330, 80 bdi-default bdi_forker_task (process_timeout)
109D, 15 events/0 neigh_periodic_work (delayed_work_timer_fn)
27D, 15 events/0 rt_worker_func (delayed_work_timer_fn)
26, 4 sirq-timer/0 dev_watchdog (dev_watchdog)
26, 4 sirq-timer/0 dev_watchdog (dev_watchdog)
13, 4 sirq-timer/0 peer_check_expire (peer_check_expire)
5, 15 events/0 rekey_seq_generator (delayed_work_timer_fn)
2, 4 sirq-timer/0 inet_frag_secret_rebuild
(inet_frag_secret_rebuild)
1D, 4 sirq-timer/0 rt_secret_rebuild (rt_secret_rebuild)
1661345 total events, 1003.107 events/sec
Board 2 (wifi -> eth) :
-----------------------
Sample period: 1649.636 s
1649636, 4 sirq-timer/0 hrtimer_start_range_ns (tick_sched_timer)
1650, 4 sirq-timer/0 __enqueue_rt_entity (sched_rt_period_timer)
1644, 15 events/0 phy_state_machine (delayed_work_timer_fn)
1644, 15 events/0 msleep (process_timeout)
822, 15 events/0 msleep (process_timeout)
329, 80 bdi-default bdi_forker_task (process_timeout)
274, 4 sirq-timer/0 arm_supers_timer (sync_supers_timer_fn)
108D, 15 events/0 neigh_periodic_work (delayed_work_timer_fn)
27, 4 sirq-timer/0 dev_watchdog (dev_watchdog)
27, 4 sirq-timer/0 dev_watchdog (dev_watchdog)
26D, 15 events/0 rt_worker_func (delayed_work_timer_fn)
13, 4 sirq-timer/0 peer_check_expire (peer_check_expire)
4, 15 events/0 rekey_seq_generator (delayed_work_timer_fn)
1, 4 sirq-timer/0 inet_frag_secret_rebuild
(inet_frag_secret_rebuild)
1D, 4 sirq-timer/0 rt_secret_rebuild (rt_secret_rebuild)
1656207 total events, 1003.603 events/sec
And here is my ifconfig on each board :
Board 1 (eth -> wifi) :
-----------------------
ath0 Link encap:Ethernet HWaddr 00:0B:6B:2F:9F:8A
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:3866892 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:777245292 (741.2 MiB)
br0 Link encap:Ethernet HWaddr 00:0B:6B:2F:9F:8A
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
eth0 Link encap:Ethernet HWaddr 00:10:02:0F:B8:06
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3866892 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:792712860 (755.9 MiB) TX bytes:0 (0.0 B)
Interrupt:133 Base address:0x3000
wifi0 Link encap:UNSPEC HWaddr
00-0B-6B-2F-9F-8A-00-00-00-00-00-00-00-00-00-00
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:3866892 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:199
RX bytes:0 (0.0 B) TX bytes:912586512 (870.3 MiB)
Interrupt:66
Board 2 (wifi -> eth) :
-----------------------
ath0 Link encap:Ethernet HWaddr 00:0B:6B:2F:A0:14
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3818800 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:767578800 (732.0 MiB) TX bytes:0 (0.0 B)
br0 Link encap:Ethernet HWaddr 00:0B:6B:2F:A0:14
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
eth0 Link encap:Ethernet HWaddr 00:10:02:0F:B8:05
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:3818800 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:782854000 (746.5 MiB)
Interrupt:133 Base address:0x3000
wifi0 Link encap:UNSPEC HWaddr
00-0B-6B-2F-A0-14-00-00-00-00-00-00-00-00-00-00
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3818800 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:199
RX bytes:901236800 (859.4 MiB) TX bytes:0 (0.0 B)
Interrupt:66
JM
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