I've been testign for weeks with 2.6.16-rc1 + the latency trace patch
and the longest latencies measured were 10-15ms due to the well known
rt_run_flush issue. Today I got one twice as long, when a Firefox
process with a bunch of acroreads in tabs, from a new code path.
It seems to trigger when a process with a large amount of memory swapped
out exits.
Can this be solved with a cond_resched?
preemption latency trace v1.1.5 on 2.6.16-rc1
--------------------------------------------------------------------
latency: 28130 us, #38020/38020, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0)
-----------------
| task: acroread-29870 (uid:1000 nice:0 policy:0 rt_prio:0)
-----------------
_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
Xorg-18254 0d.s2 1us : __trace_start_sched_wakeup (try_to_wake_up)
Xorg-18254 0d.s2 1us : __trace_start_sched_wakeup <<...>-29870> (73 0)
Xorg-18254 0d.s. 2us : wake_up_process (process_timeout)
Xorg-18254 0dn.2 3us < (2110048)
Xorg-18254 0dn.2 4us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 5us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 6us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 6us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 7us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 8us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 8us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 9us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 10us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 11us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 12us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 12us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 13us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 14us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 14us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 15us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 16us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 16us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 17us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 18us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 19us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 19us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 20us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 21us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 21us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 22us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 23us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 23us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 24us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 25us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 25us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 26us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 27us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 27us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 28us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 29us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 30us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 30us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 31us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 32us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 32us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 33us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 34us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 35us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 35us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 36us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 37us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 37us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 38us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 39us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.2 40us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 40us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 41us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 42us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 42us : radix_tree_lookup (find_trylock_page)
[ etc ]
Xorg-18254 0dn.2 28062us : free_swap_and_cache (unmap_vmas)
Xorg-18254 0dn.2 28062us : swap_info_get (free_swap_and_cache)
Xorg-18254 0dn.3 28063us : swap_entry_free (free_swap_and_cache)
Xorg-18254 0dn.3 28064us : find_trylock_page (free_swap_and_cache)
Xorg-18254 0dn.4 28064us : radix_tree_lookup (find_trylock_page)
Xorg-18254 0dn.3 28065us : preempt_schedule (find_trylock_page)
Xorg-18254 0dn.2 28066us : preempt_schedule (free_swap_and_cache)
Xorg-18254 0dn.1 28067us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28073us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28077us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28083us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28089us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28095us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28099us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28101us+: preempt_schedule (unmap_vmas)
Xorg-18254 0dn.1 28106us : preempt_schedule (unmap_vmas)
Xorg-18254 0dn.2 28107us : vm_normal_page (unmap_vmas)
Xorg-18254 0dn.2 28109us : vm_normal_page (unmap_vmas)
Xorg-18254 0dn.2 28109us : vm_normal_page (unmap_vmas)
Xorg-18254 0dn.2 28110us : vm_normal_page (unmap_vmas)
Xorg-18254 0dn.1 28111us : preempt_schedule (unmap_vmas)
Xorg-18254 0dn.. 28112us : preempt_schedule (unmap_vmas)
Xorg-18254 0dn.. 28113us : schedule (preempt_schedule)
Xorg-18254 0dn.. 28113us : stop_trace (schedule)
Xorg-18254 0dn.. 28114us : profile_hit (schedule)
Xorg-18254 0dn.1 28115us+: sched_clock (schedule)
Xorg-18254 0dn.2 28117us : recalc_task_prio (schedule)
Xorg-18254 0dn.2 28119us+: effective_prio (recalc_task_prio)
<...>-29870 0d..2 28123us+: __switch_to (schedule)
<...>-29870 0d..2 28126us : schedule <Xorg-18254> (76 73)
<...>-29870 0d..1 28127us : trace_stop_sched_switched (schedule)
<...>-29870 0d..2 28128us : trace_stop_sched_switched <<...>-29870> (73 0)
<...>-29870 0d..2 28130us : schedule (schedule)
vim:ft=help
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