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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> + Thomas Gleixner <[EMAIL PROTECTED]> + Joe Korty <[EMAIL PROTECTED]> +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. + + The contents of per-CPU hrtimer data fields not + associated with a particular cpu clock (ie, shared by + 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 + 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: + + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html