linux-ext4 - Re: [Regression] Filesystem I/O is CPU-bound in rc7 and rc8

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Message-ID: <m3d403632g.fsf@lugabout.jhcloos.org>
Date:	Wed, 17 Feb 2010 15:04:47 -0500
From:	James Cloos <cloos@...loos.com>
To:	linux-kernel@...r.kernel.org
Cc:	Chris Mason <chris.mason@...cle.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-btrfs@...r.kernel.org, jfs-discussion@...ts.sourceforge.net
Subject: Re: [Regression] Filesystem I/O is CPU-bound in rc7 and rc8

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@...loos.com>         OpenPGP: 1024D/ED7DAEA6
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