linux-kernel - [PATCH 0/4] /proc/schedstat and /proc/sched

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Date:	Tue, 11 Dec 2012 13:50:01 -0600
From:	Nathan Zimmer <nzimmer@....com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	davej@...hat.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	johnstul@...ibm.com, viro@...iv.linux.org.uk, peterz@...radead.org,
	mingo@...hat.com, Nathan Zimmer <nzimmer@....com>
Subject: [PATCH 0/4] /proc/schedstat and /proc/sched_debug fail at 4096

When running with 4096 cores attemping to read /proc/schedstat,
/proc/sched_debug, /proc/timer_list will fail with an ENOMEM condition.
On a sufficantly large systems the total amount of data is more then 4mb, so
it won't fit into a single buffer.  The failure can also occur on smaller
systems when memory fragmentation is high.

An solution considered but not tried for sched_stat and scheddebug would to be
create an alternative mechanism to single_open but rather then calling *_show
once it calls show once per possible cpu.  If someone feels strongly that is
the way to go I can give it a spin.

Nathan Zimmer (4):
  procfs: /proc/sched_stat fails on very very large machines.
  procfs: /proc/sched_debug fails on very very large machines.
  /proc/timer_list split timer_list_show_tickdevices
  Convert timer list to be a proper seq_file.

 kernel/sched/debug.c     |   84 +++++++++++++++++++++++++++++++++-----
 kernel/sched/stats.c     |   73 ++++++++++++++++++++++++---------
 kernel/time/timer_list.c |  102 +++++++++++++++++++++++++++++++++++++---------
 3 files changed, 209 insertions(+), 50 deletions(-)

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