Messages in this thread | | | Date | Fri, 05 Dec 2008 09:12:18 -0800 | From | Randy Dunlap <> | Subject | Re: [PATCH] ABI Documentation for /proc/timer_list, v2 |
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Joe Korty wrote: > Document /proc/timer_list ABI, version 2. > > This partially documents /timer_list, including the > proposed 'Version 0.5' extensions that add a jiffie timer > display. > > v2 exists to address some of the concerns Michael Kerrisk > brought up. What was left out: I did not document old > versions of /timer_list, I did not document the meaning > of the x.y version numbering system (which only Ingo > can answer anyway), and I did not document fields of > secondary importance that already had adequate 'DocBook' > documentation in the kernel sources. > > Signed-off-by: Joe Korty <joe.korty@ccur.com> > > Index: 2.6.28-rc6/Documentation/ABI/stable/procfs-timer_list > =================================================================== > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > +++ 2.6.28-rc6/Documentation/ABI/stable/procfs-timer_list 2008-12-01 13:07:15.000000000 -0500 > @@ -0,0 +1,129 @@ > +What: /proc/timer_list > +Date: November 2008 > +Contact: Ingo Molnar <mingo@elte.hu> > + Thomas Gleixner <tglx@linutronix.de> > + Joe Korty <joe.korty@ccur.com> > +Revision-Rate: Moderate > +At-Revision: 0.5 > +Description: > + /proc/timer_list displays most everything about every kind > + of timer, and some things about time too. > + > + The contents of this file should be expected to change, > + as the data displayed corresponds directly to various > + kernel-internal data structures. For this reason, the first > + line contains the file revision. It is the responsibility > + of this file's maintainers to bump the revision each time a > + kernel is released having incompatible changes in this file. > + > + This document covers only the version of /proc/timer_list > + located in the kernel sources to which it is attached. > + Documentation for previous (and later) versions of > + /proc/timer_list is to be found (if they exist) in the > + kernel sources of those earlier (or later) kernels. > + > + Section Overview > + ---------------- > + The file contains several somewhat independent sections. > + > + The first section contains a few lines of global info: > + 1 - Timer List Version: File revision. > + 2 - HRTIMER_MAX_CLOCK_BASES: number of clock types that > + support high resolution timers. > + 3 - now at x nsecs: number of nsecs since boot. > + > + The second section is organized per-CPU. Each CPU subsection > + in turn contains several sub-subsections which are, in order > + of appearance: > + > + The contents of the data structures associated with each > + clock on this CPU: > + 1 - clock ID: 0 == CLOCK_REALTIME, 1 == CLOCK_MONOTONIC > + 2 - base: kernel address of this clock's > + hrtimer_clock_base structure. > + 3 - resolution: resolution of this clock. > + 4 - get_time: name of kernel function used to fetch > + time from this clock. > + 5 - offset: difference, in nsecs, between this clock > + and the reference clock for this clock. > + Under each of these clocks is, in turn, a display of all > + the active high resolution timers queued to that clock. > + These are the lines beginning with '#' and are described > + in detail later in this document.
Are we supposed to be able to see lines beginning with '#' in this text file, or only in /proc/timer_list ?
> + > + The contents of per-CPU hrtimer data fields not > + associated with a particular cpu clock (ie, shared by
Please use "CPU" consistenly (instead of "cpu").
> + both clocks or not associated with any clock). These > + are: expires_next, hres_active, nr_event, nohz_mode, all > + things idle_*, tick_stopped, last_jiffies, next_jiffies. > + The above are field names from 'struct tick_sched' and > + 'struct hrtimer_cpu_base', documentation for these may
'struct hrtimer_cpu_base'; documentation for these may
> + be found in the kernel DocBook. > + > + A display of low resolution (ie, jiffie) timer wheel > + data. These are prefixed by the lines: > + 1 - base: kernel virtual address of the timer wheel > + data structure (struct tvec_base) for this cpu. > + 2 - running timer: kernel virtual address of the > + expired timer being processed, NULL if none. > + 3 - timer_jiffies: what this wheel considers to > + be the current time, will be == jiffies or > + will lag it by a tick or two if it has not > + caught up with the current time. > + Also under this section is a display, one per line, of > + each active jiffie timer queued to this CPU. These are > + the lines under an 'active jiffie timers' section that > + begin with a number. > + > + The third and final section describes each 'tick device' > + known to the kernel. A tick device is a piece of hardware > + capable of generating periodic and/or one-shot interrupts > + under software control, and thus is capable of generating > + the interrupts needed to expire the various active timers > + at their given expiration times. Examples of tick devices: > + hpet, pit, lapic. All but the first two lines display > + fields corresponding to structure elements from 'struct > + clock_event_device', documentation for which can be found > + in the kernel Docbook. The first two lines are: > + 1 - mode: 0 == periodic timer, 1 == one-shot timer > + 2 - is 'Per CPU device' or is 'Broadcast device' > + > + Hires Timer Layout > + ------------------ > + High-resolution timers are displayed on lines that begin > + with a '#' and always appear under one of the many sections > + labeled 'active timers'. There is an 'active timers' > + section for every CPU and every clock. > + > + The fields of a hrtimer, spread out over two lines, are:
an hrtimer, > + > + line 1 fields: > + 1 - unique hrtimer index (#0, #1, #2, etc) > + 2 - kernel address of the hrtimer data structure > + in question > + 3 - function to be called when timer expires > + 4 - timer state (eg, S:01), avail states, OR-able: > + 0 - inactive > + 1 - enqueued > + 2 - callback > + 4 - pending > + 8 - migrate > + 5 - function which created the timer > + 6 - process name & pid which created the timer > + > + line 2 fields: > + 1 - absolute expiration time, range format (start - end) > + 2 - relative expiration time, range format (start - end) > + > + Lowres Timer Layout > + ------------------- > + Low-resolution timers are displayed one-per-line under > + sections labeled 'active jiffie timers'. There is one such > + section per CPU. A lowres timer has the following fields: > + > + 1 - number of jiffies remaining until timer expires > + 2 - function to be called on expiration > + 3 - data value to be given to the above function on > + expiration > + 4 - function which created this timer > + 5 - name & pid of the process that created this timer
Thanks, ~Randy
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