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SubjectRe: [Regression] Filesystem I/O is CPU-bound in rc7 and rc8
Date
While getting re-aquainted with perf, and after upgrading to the current
version, I see that do_page_fault, unmap_vmas, get_page_from_freelist,
handle_mm_fault, __do_fault and T.1339 tend to get the most time when the
kernel is spinning.

T.1339 is in this part of kallsyms:

,----< grep -E -C9 ^c1027750 /proc/kallsyms >
| c10266a0 T sched_setscheduler_nocheck
| c10266c0 T sched_setscheduler
| c10266e0 t do_sched_setscheduler
| c1026770 T sys_sched_setparam
| c1026790 T sys_sched_setscheduler
| c10267c0 T sched_fork
| c1026900 T task_oncpu_function_call
| c1026960 T print_cfs_rq
| c1027640 T scheduler_tick
| c1027750 t T.1339
| c10277f0 T schedule_tail
| c1027830 t ftrace_raw_output_sched_kthread_stop
| c1027930 t ftrace_raw_output_sched_kthread_stop_ret
| c1027a30 t ftrace_raw_output_sched_wait_task
| c1027b40 t ftrace_raw_output_sched_switch
| c1027c90 t ftrace_raw_output_sched_migrate_task
| c1027da0 t ftrace_raw_output_sched_process_wait
| c1027eb0 t ftrace_raw_output_sched_process_fork
| c1027fc0 t ftrace_raw_output_sched_stat_runtime
`----
suggesting that T.1339 is part of sched.

This leaves the impression that the issue is related to either
scheduling or paging.

I don't see any commits in the rc6..rc7 timeframe which stand out
as likely suspects.

-JimC
--
James Cloos <cloos@jhcloos.com> OpenPGP: 1024D/ED7DAEA6


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