Ingo Molnar wrote:
i have released the -V0.7.48-00 Real-Time Preemption patch, which can be
downloaded from the usual place:
With -V0.7.48-01 I get interestingly long latency traces. For example
this one is 277 us. This is on i386. I've put the full trace to:
http://www.uamt.feec.vutbr.cz/rizeni/pom/latency_trace-RT-V0.7.48-01.txt
Because of the presence of __wake_up_sync there, I'd guess it has
something to do with the NEED_RESCHED_DELAYED thing.
Here's an excerpt of it:
preemption latency trace v1.1.4 on 2.6.12-rc6-RT-V0.7.48-01
--------------------------------------------------------------------
latency: 277 us, #2349/2349, CPU#0 | (M:rt VP:0, KP:1, SP:1 HP:1 #P:1)
-----------------
| task: XFree86-5780 (uid:0 nice:-10 policy:0 rt_prio:0)
-----------------
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
mozilla--6007 0Dnh2 0us!: <697a6f6d> (<2d616c6c>)
mozilla--6007 0Dnh2 0us : __trace_start_sched_wakeup (try_to_wake_up)
mozilla--6007 0.... 0us : _spin_unlock_irqrestore (__wake_up_sync)
mozilla--6007 0.... 0us : up_mutex (__wake_up_sync)
mozilla--6007 0.... 0us : __up_mutex (up_mutex)
mozilla--6007 0.... 0us : _read_unlock (sock_wfree)
mozilla--6007 0.... 0us : up_read_mutex (sock_wfree)
mozilla--6007 0.... 1us : up_write_mutex (sock_wfree)
mozilla--6007 0.... 1us : __up_mutex (up_write_mutex)
mozilla--6007 0.... 1us : kfree_skbmem (unix_stream_recvmsg)
mozilla--6007 0.... 1us : skb_release_data (kfree_skbmem)
mozilla--6007 0.... 1us : kfree (kfree_skbmem)
mozilla--6007 0.... 1us : __local_save_flags (kfree)
mozilla--6007 0.... 1us : _spin_lock (kfree)
mozilla--6007 0.... 2us : __spin_lock (_spin_lock)
mozilla--6007 0.... 2us : __might_sleep (__spin_lock)
mozilla--6007 0.... 2us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 2us : _down_mutex (__spin_lock)
mozilla--6007 0.... 2us : __down_mutex (__spin_lock)
mozilla--6007 0...1 2us : grab_lock (__down_mutex)
mozilla--6007 0...1 2us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 2us : _spin_unlock (kfree)
mozilla--6007 0.... 2us : up_mutex (kfree)
mozilla--6007 0.... 3us : __up_mutex (up_mutex)
mozilla--6007 0.... 3us : kmem_cache_free (kfree_skbmem)
mozilla--6007 0.... 3us : __local_save_flags (kmem_cache_free)
mozilla--6007 0.... 3us : _spin_lock (kmem_cache_free)
mozilla--6007 0.... 3us : __spin_lock (_spin_lock)
mozilla--6007 0.... 3us : __might_sleep (__spin_lock)
mozilla--6007 0.... 3us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 3us : _down_mutex (__spin_lock)
mozilla--6007 0.... 3us : __down_mutex (__spin_lock)
mozilla--6007 0...1 4us : grab_lock (__down_mutex)
mozilla--6007 0...1 4us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 4us : _spin_unlock (kmem_cache_free)
mozilla--6007 0.... 4us : up_mutex (kmem_cache_free)
mozilla--6007 0.... 4us : __up_mutex (up_mutex)
mozilla--6007 0.... 4us : skb_dequeue (unix_stream_recvmsg)
mozilla--6007 0.... 4us : _spin_lock_irqsave (skb_dequeue)
mozilla--6007 0.... 4us : __spin_lock (_spin_lock_irqsave)
mozilla--6007 0.... 5us : __might_sleep (__spin_lock)
mozilla--6007 0.... 5us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 5us : _down_mutex (__spin_lock)
mozilla--6007 0.... 5us : __down_mutex (__spin_lock)
mozilla--6007 0...1 5us : grab_lock (__down_mutex)
mozilla--6007 0...1 5us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 5us : __local_save_flags (_spin_lock_irqsave)
mozilla--6007 0.... 5us : _spin_unlock_irqrestore (skb_dequeue)
.
.
.
mozilla--6007 0.... 268us : __wake_up_common (__wake_up_sync)
mozilla--6007 0.... 268us : default_wake_function (__wake_up_common)
mozilla--6007 0.... 268us : try_to_wake_up (__wake_up_common)
mozilla--6007 0.... 268us : _spin_unlock_irqrestore (__wake_up_sync)
mozilla--6007 0.... 268us : up_mutex (__wake_up_sync)
mozilla--6007 0.... 269us : __up_mutex (up_mutex)
mozilla--6007 0.... 269us : _read_unlock (sock_wfree)
mozilla--6007 0.... 269us : up_read_mutex (sock_wfree)
mozilla--6007 0.... 269us : up_write_mutex (sock_wfree)
mozilla--6007 0.... 269us : __up_mutex (up_write_mutex)
mozilla--6007 0.... 269us : kfree_skbmem (unix_stream_recvmsg)
mozilla--6007 0.... 269us : skb_release_data (kfree_skbmem)
mozilla--6007 0.... 269us : kfree (kfree_skbmem)
mozilla--6007 0.... 270us : __local_save_flags (kfree)
mozilla--6007 0.... 270us : _spin_lock (kfree)
mozilla--6007 0.... 270us : __spin_lock (_spin_lock)
mozilla--6007 0.... 270us : __might_sleep (__spin_lock)
mozilla--6007 0.... 270us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 270us : _down_mutex (__spin_lock)
mozilla--6007 0.... 270us : __down_mutex (__spin_lock)
mozilla--6007 0...1 270us : grab_lock (__down_mutex)
mozilla--6007 0...1 270us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 270us : _spin_unlock (kfree)
mozilla--6007 0.... 271us : up_mutex (kfree)
mozilla--6007 0.... 271us : __up_mutex (up_mutex)
mozilla--6007 0.... 271us : kmem_cache_free (kfree_skbmem)
mozilla--6007 0.... 271us : __local_save_flags (kmem_cache_free)
mozilla--6007 0.... 271us : _spin_lock (kmem_cache_free)
mozilla--6007 0.... 271us : __spin_lock (_spin_lock)
mozilla--6007 0.... 271us : __might_sleep (__spin_lock)
mozilla--6007 0.... 271us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 271us : _down_mutex (__spin_lock)
mozilla--6007 0.... 271us : __down_mutex (__spin_lock)
mozilla--6007 0...1 272us : grab_lock (__down_mutex)
mozilla--6007 0...1 272us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 272us : _spin_unlock (kmem_cache_free)
mozilla--6007 0.... 272us : up_mutex (kmem_cache_free)
mozilla--6007 0.... 272us : __up_mutex (up_mutex)
mozilla--6007 0.... 272us : rt_up (unix_stream_recvmsg)
mozilla--6007 0...1 272us : __up_mutex (rt_up)
mozilla--6007 0.... 273us : dnotify_parent (vfs_read)
mozilla--6007 0.... 273us : _spin_lock (dnotify_parent)
mozilla--6007 0.... 273us : __spin_lock (_spin_lock)
mozilla--6007 0.... 273us : __might_sleep (__spin_lock)
mozilla--6007 0.... 273us : irqs_disabled (__might_sleep)
mozilla--6007 0.... 273us : _down_mutex (__spin_lock)
mozilla--6007 0.... 273us : __down_mutex (__spin_lock)
mozilla--6007 0...1 273us : grab_lock (__down_mutex)
mozilla--6007 0...1 274us : __down_mutex <mozilla--6007> (7d 0)
mozilla--6007 0.... 274us : _spin_unlock (vfs_read)
mozilla--6007 0.... 274us : up_mutex (vfs_read)
mozilla--6007 0.... 274us : __up_mutex (up_mutex)
mozilla--6007 0.... 274us : fput (sys_read)
mozilla--6007 0Dnh. 274us : __schedule (work_resched)
mozilla--6007 0Dnh. 275us : profile_hit (__schedule)
mozilla--6007 0Dnh1 275us : sched_clock (__schedule)
mozilla--6007 0Dnh1 275us : local_irq_disable (__schedule)
<...>-5780 0dnh2 276us : __switch_to (__schedule)
<...>-5780 0dnh2 276us : __schedule <mozilla--6007> (7d 73)
<...>-5780 0dnh1 276us : trace_stop_sched_switched (__schedule)
<...>-5780 0dnh1 276us : trace_stop_sched_switched <<...>-5780> (73 0)
<...>-5780 0dnh1 277us : trace_stop_sched_switched (__schedule)
-
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