summaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
authorKees Cook <keescook@chromium.org>2017-02-08 11:26:59 -0800
committerThomas Gleixner <tglx@linutronix.de>2017-02-10 11:15:08 +0100
commitdfb4357da6ddbdf57d583ba64361c9d792b0e0b1 (patch)
tree52d625e15accaf3c1b3e0504e64e6021c9f8b091 /Documentation
parentbb42ca47401010fc02901b5e8f79e40a26f208cb (diff)
time: Remove CONFIG_TIMER_STATS
Currently CONFIG_TIMER_STATS exposes process information across namespaces: kernel/time/timer_list.c print_timer(): SEQ_printf(m, ", %s/%d", tmp, timer->start_pid); /proc/timer_list: #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570 Given that the tracer can give the same information, this patch entirely removes CONFIG_TIMER_STATS. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: John Stultz <john.stultz@linaro.org> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: linux-doc@vger.kernel.org Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Xing Gao <xgao01@email.wm.edu> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Jessica Frazelle <me@jessfraz.com> Cc: kernel-hardening@lists.openwall.com Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Michal Marek <mmarek@suse.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Olof Johansson <olof@lixom.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-api@vger.kernel.org Cc: Arjan van de Ven <arjan@linux.intel.com> Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/timers/timer_stats.txt73
1 files changed, 0 insertions, 73 deletions
diff --git a/Documentation/timers/timer_stats.txt b/Documentation/timers/timer_stats.txt
deleted file mode 100644
index de835ee97455..000000000000
--- a/Documentation/timers/timer_stats.txt
+++ /dev/null
@@ -1,73 +0,0 @@
-timer_stats - timer usage statistics
-------------------------------------
-
-timer_stats is a debugging facility to make the timer (ab)usage in a Linux
-system visible to kernel and userspace developers. If enabled in the config
-but not used it has almost zero runtime overhead, and a relatively small
-data structure overhead. Even if collection is enabled runtime all the
-locking is per-CPU and lookup is hashed.
-
-timer_stats should be used by kernel and userspace developers to verify that
-their code does not make unduly use of timers. This helps to avoid unnecessary
-wakeups, which should be avoided to optimize power consumption.
-
-It can be enabled by CONFIG_TIMER_STATS in the "Kernel hacking" configuration
-section.
-
-timer_stats collects information about the timer events which are fired in a
-Linux system over a sample period:
-
-- the pid of the task(process) which initialized the timer
-- the name of the process which initialized the timer
-- the function where the timer was initialized
-- the callback function which is associated to the timer
-- the number of events (callbacks)
-
-timer_stats adds an entry to /proc: /proc/timer_stats
-
-This entry is used to control the statistics functionality and to read out the
-sampled information.
-
-The timer_stats functionality is inactive on bootup.
-
-To activate a sample period issue:
-# echo 1 >/proc/timer_stats
-
-To stop a sample period issue:
-# echo 0 >/proc/timer_stats
-
-The statistics can be retrieved by:
-# cat /proc/timer_stats
-
-While sampling is enabled, each readout from /proc/timer_stats will see
-newly updated statistics. Once sampling is disabled, the sampled information
-is kept until a new sample period is started. This allows multiple readouts.
-
-Sample output of /proc/timer_stats:
-
-Timerstats sample period: 3.888770 s
- 12, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
- 15, 1 swapper hcd_submit_urb (rh_timer_func)
- 4, 959 kedac schedule_timeout (process_timeout)
- 1, 0 swapper page_writeback_init (wb_timer_fn)
- 28, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
- 22, 2948 IRQ 4 tty_flip_buffer_push (delayed_work_timer_fn)
- 3, 3100 bash schedule_timeout (process_timeout)
- 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
- 1, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
- 1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
- 1, 2292 ip __netdev_watchdog_up (dev_watchdog)
- 1, 23 events/1 do_cache_clean (delayed_work_timer_fn)
-90 total events, 30.0 events/sec
-
-The first column is the number of events, the second column the pid, the third
-column is the name of the process. The forth column shows the function which
-initialized the timer and in parenthesis the callback function which was
-executed on expiry.
-
- Thomas, Ingo
-
-Added flag to indicate 'deferrable timer' in /proc/timer_stats. A deferrable
-timer will appear as follows
- 10D, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
-