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timers: split process wide cpu clocks/timers

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Change the process wide cpu timers/clocks so that we:

 1) don't mess up the kernel with too many threads,
 2) don't have a per-cpu allocation for each process,
 3) have no impact when not used.

In order to accomplish this we're going to split it into two parts:

 - clocks; which can take all the time they want since they run
           from user context -- ie. sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID)

 - timers; which need constant time sampling but since they're
           explicity used, the user can pay the overhead.

The clock readout will go back to a full sum of the thread group, while the
timers will run of a global 'clock' that only runs when needed, so only
programs that make use of the facility pay the price.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-02-05 12:24:16 +01:00 • committed by Ingo Molnar
parent 32bd671d6c
commit 4cd4c1b40d
5 changed files with 155 additions and 54 deletions
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54
include/linux/sched.h
View file

@ -443,7 +443,6 @@ struct pacct_struct {
* @utime: time spent in user mode, in &cputime_t units
* @stime: time spent in kernel mode, in &cputime_t units
* @sum_exec_runtime: total time spent on the CPU, in nanoseconds
* @lock: lock for fields in this struct
*
* This structure groups together three kinds of CPU time that are
* tracked for threads and thread groups. Most things considering
@ -454,23 +453,33 @@ struct task_cputime {
cputime_t utime;
cputime_t stime;
unsigned long long sum_exec_runtime;
spinlock_t lock;
};
/* Alternate field names when used to cache expirations. */
#define prof_exp stime
#define virt_exp utime
#define sched_exp sum_exec_runtime
#define INIT_CPUTIME \
(struct task_cputime) { \
.utime = cputime_zero, \
.stime = cputime_zero, \
.sum_exec_runtime = 0, \
}
/**
* struct thread_group_cputime - thread group interval timer counts
* @totals: thread group interval timers; substructure for
* uniprocessor kernel, per-cpu for SMP kernel.
* struct thread_group_cputimer - thread group interval timer counts
* @cputime: thread group interval timers.
* @running: non-zero when there are timers running and
* @cputime receives updates.
* @lock: lock for fields in this struct.
*
* This structure contains the version of task_cputime, above, that is
* used for thread group CPU clock calculations.
* used for thread group CPU timer calculations.
*/
struct thread_group_cputime {
struct task_cputime totals;
struct thread_group_cputimer {
struct task_cputime cputime;
int running;
spinlock_t lock;
};
/*
@ -519,10 +528,10 @@ struct signal_struct {
cputime_t it_prof_incr, it_virt_incr;
/*
* Thread group totals for process CPU clocks.
* See thread_group_cputime(), et al, for details.
* Thread group totals for process CPU timers.
* See thread_group_cputimer(), et al, for details.
*/
struct thread_group_cputime cputime;
struct thread_group_cputimer cputimer;
/* Earliest-expiration cache. */
struct task_cputime cputime_expires;
@ -2191,27 +2200,26 @@ static inline int spin_needbreak(spinlock_t *lock)
/*
* Thread group CPU time accounting.
*/
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
static inline
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct task_cputime *totals = &tsk->signal->cputime.totals;
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
unsigned long flags;
spin_lock_irqsave(&totals->lock, flags);
*times = *totals;
spin_unlock_irqrestore(&totals->lock, flags);
WARN_ON(!cputimer->running);
spin_lock_irqsave(&cputimer->lock, flags);
*times = cputimer->cputime;
spin_unlock_irqrestore(&cputimer->lock, flags);
}
static inline void thread_group_cputime_init(struct signal_struct *sig)
{
sig->cputime.totals = (struct task_cputime){
.utime = cputime_zero,
.stime = cputime_zero,
.sum_exec_runtime = 0,
};
spin_lock_init(&sig->cputime.totals.lock);
sig->cputimer.cputime = INIT_CPUTIME;
spin_lock_init(&sig->cputimer.lock);
sig->cputimer.running = 0;
}
static inline void thread_group_cputime_free(struct signal_struct *sig)