Hi,
While running iozone, I notice severe stalls of vmstat output
despite vmstat running SCHED_RR and mlockall().
With IKD, I ran a million line ktrace of such a stall, and find
no occurance of vmstat's pid. (trace covers a ~full second of
kernel time) The only user process which was scheduled during
this second was iozone itself (p262). I have seen such stalls
last for ~5 seconds.
%TOT_TIME TOT_USECS AVG/CALL NCALLS KADDR FUNCTION PID
0.0002% 2.15 2.15 1 c01077db __switch_to p4
0.0025% 24.18 2.69 9 c01077db __switch_to p262
0.0043% 41.91 0.86 49 c01077db __switch_to p0
0.0049% 47.54 2.97 16 c01077db __switch_to p3
0.0107% 102.83 1.80 57 c01077db __switch_to p6
Tail end of profile of this trace by pid:
%TOT_TIME TOT_USECS AVG/CALL NCALLS KADDR FUNCTION PID
0.2485% 2394.91 1.22 1964 c0108fea ret_from_sys_call p262
0.2496% 2405.70 0.61 3925 c0134f8b get_hash_table p262
0.2555% 2462.40 0.31 7854 c0135052 buffer_insert_inode_queue p262
0.2731% 2632.40 0.65 4029 c01a9bc7 ide_do_request p6
0.3339% 3218.32 0.85 3788 c012bdd0 kmem_cache_alloc p262
0.3899% 3757.91 0.18 21110 c012f1ee nr_free_pages p262
0.4086% 3937.88 0.50 7848 c013573f getblk p262
0.4385% 4225.65 0.32 13255 c011612a wake_up_process p262
0.5245% 5055.25 0.24 21110 c012f23a nr_inactive_clean_pages p262
0.5468% 5269.94 9.38 562 c012d017 swap_out p4
0.7403% 7134.44 1.76 4046 c018a907 elevator_linus_merge p6
2.8165% 27144.72 0.54 50589 c0137527 try_to_free_buffers p4
3.1803% 30650.25 43.05 712 c0111caa apm_bios_call_simple p3
3.8435% 37041.89 0.20 185504 c012cbf7 try_to_swap_out p4
5.0470% 48641.41 0.95 51157 c012f179 __free_pages p4
9.8731% 95152.96 0.54 177443 c0137527 try_to_free_buffers p6
10.7010% 103132.39 26.28 3925 c020bb80 __generic_copy_from_user p262
17.5982% 169604.69 0.94 180429 c012f179 __free_pages p6
33.8960% 326677.23 2916.76 112 c0107171 default_idle p0
1048352 entries; 963762.98 total usecs.
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