minix/kernel/clock.c
Tomas Hruby 1b56fdb33c Time accounting based on TSC
- as thre are still KERNEL and IDLE entries, time accounting for
  kernel and idle time works the same as for any other process

- everytime we stop accounting for the currently running process,
  kernel or idle, we read the TSC counter and increment the p_cycles
  entry.

- the process cycles inherently include some of the kernel cycles as
  we can stop accounting for the process only after we save its
  context and we start accounting just before we restore its context

- this assumes that the system does not scale the CPU frequency which
  will be true for ... long time ;-)
2010-02-10 15:36:54 +00:00

269 lines
8.7 KiB
C

/* This file contains the clock task, which handles time related functions.
* Important events that are handled by the CLOCK include setting and
* monitoring alarm timers and deciding when to (re)schedule processes.
* The CLOCK offers a direct interface to kernel processes. System services
* can access its services through system calls, such as sys_setalarm(). The
* CLOCK task thus is hidden from the outside world.
*
* Changes:
* Aug 18, 2006 removed direct hardware access etc, MinixPPC (Ingmar Alting)
* Oct 08, 2005 reordering and comment editing (A. S. Woodhull)
* Mar 18, 2004 clock interface moved to SYSTEM task (Jorrit N. Herder)
* Sep 30, 2004 source code documentation updated (Jorrit N. Herder)
* Sep 24, 2004 redesigned alarm timers (Jorrit N. Herder)
*
* Clock task is notified by the clock's interrupt handler when a timer
* has expired.
*
* In addition to the main clock_task() entry point, which starts the main
* loop, there are several other minor entry points:
* clock_stop: called just before MINIX shutdown
* get_uptime: get realtime since boot in clock ticks
* set_timer: set a watchdog timer (+)
* reset_timer: reset a watchdog timer (+)
* read_clock: read the counter of channel 0 of the 8253A timer
*
* (+) The CLOCK task keeps tracks of watchdog timers for the entire kernel.
* It is crucial that watchdog functions not block, or the CLOCK task may
* be blocked. Do not send() a message when the receiver is not expecting it.
* Instead, notify(), which always returns, should be used.
*/
#include "kernel.h"
#include "proc.h"
#include <minix/com.h>
#include <minix/endpoint.h>
#include "clock.h"
#ifdef CONFIG_WATCHDOG
#include "watchdog.h"
#endif
/* Function prototype for PRIVATE functions.
*/
FORWARD _PROTOTYPE( void load_update, (void));
/* The CLOCK's timers queue. The functions in <timers.h> operate on this.
* Each system process possesses a single synchronous alarm timer. If other
* kernel parts want to use additional timers, they must declare their own
* persistent (static) timer structure, which can be passed to the clock
* via (re)set_timer().
* When a timer expires its watchdog function is run by the CLOCK task.
*/
PRIVATE timer_t *clock_timers; /* queue of CLOCK timers */
PRIVATE clock_t next_timeout; /* realtime that next timer expires */
/* The time is incremented by the interrupt handler on each clock tick.
*/
PRIVATE clock_t realtime = 0; /* real time clock */
/*===========================================================================*
* init_clock *
*===========================================================================*/
PUBLIC void clock_init()
{
/* Set a watchdog timer to periodically balance the scheduling queues.
Side-effect sets new timer */
balance_queues(NULL);
}
/*
* The boot processor timer interrupt handler. In addition to non-boot cpus it
* keeps real time and notifies the clock task if need be
*/
PUBLIC int bsp_timer_int_handler(void)
{
unsigned ticks;
if(minix_panicing)
return 0;
/* Get number of ticks and update realtime. */
ticks = lost_ticks + 1;
lost_ticks = 0;
realtime += ticks;
ap_timer_int_handler();
/* if a timer expired, notify the clock task */
if ((next_timeout <= realtime)) {
tmrs_exptimers(&clock_timers, realtime, NULL);
next_timeout = (clock_timers == NULL) ?
TMR_NEVER : clock_timers->tmr_exp_time;
}
if (do_serial_debug)
do_ser_debug();
return(1); /* reenable interrupts */
}
/*===========================================================================*
* get_uptime *
*===========================================================================*/
PUBLIC clock_t get_uptime(void)
{
/* Get and return the current clock uptime in ticks. */
return(realtime);
}
/*===========================================================================*
* set_timer *
*===========================================================================*/
PUBLIC void set_timer(tp, exp_time, watchdog)
struct timer *tp; /* pointer to timer structure */
clock_t exp_time; /* expiration realtime */
tmr_func_t watchdog; /* watchdog to be called */
{
/* Insert the new timer in the active timers list. Always update the
* next timeout time by setting it to the front of the active list.
*/
tmrs_settimer(&clock_timers, tp, exp_time, watchdog, NULL);
next_timeout = clock_timers->tmr_exp_time;
}
/*===========================================================================*
* reset_timer *
*===========================================================================*/
PUBLIC void reset_timer(tp)
struct timer *tp; /* pointer to timer structure */
{
/* The timer pointed to by 'tp' is no longer needed. Remove it from both the
* active and expired lists. Always update the next timeout time by setting
* it to the front of the active list.
*/
tmrs_clrtimer(&clock_timers, tp, NULL);
next_timeout = (clock_timers == NULL) ?
TMR_NEVER : clock_timers->tmr_exp_time;
}
/*===========================================================================*
* load_update *
*===========================================================================*/
PRIVATE void load_update(void)
{
u16_t slot;
int enqueued = 0, q;
struct proc *p;
/* Load average data is stored as a list of numbers in a circular
* buffer. Each slot accumulates _LOAD_UNIT_SECS of samples of
* the number of runnable processes. Computations can then
* be made of the load average over variable periods, in the
* user library (see getloadavg(3)).
*/
slot = (realtime / system_hz / _LOAD_UNIT_SECS) % _LOAD_HISTORY;
if(slot != kloadinfo.proc_last_slot) {
kloadinfo.proc_load_history[slot] = 0;
kloadinfo.proc_last_slot = slot;
}
/* Cumulation. How many processes are ready now? */
for(q = 0; q < NR_SCHED_QUEUES; q++)
for(p = rdy_head[q]; p != NIL_PROC; p = p->p_nextready)
enqueued++;
kloadinfo.proc_load_history[slot] += enqueued;
/* Up-to-dateness. */
kloadinfo.last_clock = realtime;
}
/*
* Timer interupt handler. This is the only thing executed on non boot
* processors. It is called by bsp_timer_int_handler() on the boot processor
*/
PUBLIC int ap_timer_int_handler(void)
{
/* Update user and system accounting times. Charge the current process
* for user time. If the current process is not billable, that is, if a
* non-user process is running, charge the billable process for system
* time as well. Thus the unbillable process' user time is the billable
* user's system time.
*/
unsigned ticks = 1;
int expired = 0;
struct proc * p, * billp;
#ifdef CONFIG_WATCHDOG
/*
* we need to know whether local timer ticks are happening or whether
* the kernel is locked up. We don't care about overflows as we only
* need to know that it's still ticking or not
*/
watchdog_local_timer_ticks++;
#endif
/* Update user and system accounting times. Charge the current process
* for user time. If the current process is not billable, that is, if a
* non-user process is running, charge the billable process for system
* time as well. Thus the unbillable process' user time is the billable
* user's system time.
*/
/* FIXME prepared for get_cpu_local_var() */
p = proc_ptr;
billp = bill_ptr;
p->p_user_time += ticks;
if (priv(p)->s_flags & PREEMPTIBLE) {
p->p_ticks_left -= ticks;
}
if (! (priv(p)->s_flags & BILLABLE)) {
billp->p_sys_time += ticks;
billp->p_ticks_left -= ticks;
}
/* Decrement virtual timers, if applicable. We decrement both the
* virtual and the profile timer of the current process, and if the
* current process is not billable, the timer of the billed process as
* well. If any of the timers expire, do_clocktick() will send out
* signals.
*/
if ((p->p_misc_flags & MF_VIRT_TIMER) &&
(p->p_virt_left -= ticks) <= 0) expired = 1;
if ((p->p_misc_flags & MF_PROF_TIMER) &&
(p->p_prof_left -= ticks) <= 0) expired = 1;
if (! (priv(p)->s_flags & BILLABLE) &&
(billp->p_misc_flags & MF_PROF_TIMER) &&
(billp->p_prof_left -= ticks) <= 0) expired = 1;
/*
* Check if a process-virtual timer expired. Check current process, but
* also bill_ptr - one process's user time is another's system time, and
* the profile timer decreases for both!
*/
vtimer_check(p);
if (p != billp)
vtimer_check(billp);
/* Update load average. */
load_update();
/* check if the process is still runnable after checking the vtimer */
if (p->p_rts_flags == 0 && p->p_ticks_left <= 0 &&
priv(p)->s_flags & PREEMPTIBLE) {
/* this dequeues the process */
RTS_SET(p, RTS_NO_QUANTUM);
}
return 1;
}
PUBLIC int boot_cpu_init_timer(unsigned freq)
{
if (arch_init_local_timer(freq))
return -1;
if (arch_register_local_timer_handler(
(irq_handler_t) bsp_timer_int_handler))
return -1;
return 0;
}