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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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11
include/linux/init_task.h
View file

@ -48,12 +48,11 @@ extern struct fs_struct init_fs;
.posix_timers = LIST_HEAD_INIT(sig.posix_timers), \
.cpu_timers = INIT_CPU_TIMERS(sig.cpu_timers), \
.rlim = INIT_RLIMITS, \
.cputime = { .totals = { \
.utime = cputime_zero, \
.stime = cputime_zero, \
.sum_exec_runtime = 0, \
.lock = __SPIN_LOCK_UNLOCKED(sig.cputime.totals.lock), \
}, }, \
.cputimer = { \
.cputime = INIT_CPUTIME, \
.running = 0, \
.lock = __SPIN_LOCK_UNLOCKED(sig.cputimer.lock), \
}, \
}
extern struct nsproxy init_nsproxy;

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)

4
kernel/itimer.c
View file

@ -62,7 +62,7 @@ int do_getitimer(int which, struct itimerval *value)
struct task_cputime cputime;
cputime_t utime;
thread_group_cputime(tsk, &cputime);
thread_group_cputimer(tsk, &cputime);
utime = cputime.utime;
if (cputime_le(cval, utime)) { /* about to fire */
cval = jiffies_to_cputime(1);
@ -82,7 +82,7 @@ int do_getitimer(int which, struct itimerval *value)
struct task_cputime times;
cputime_t ptime;
thread_group_cputime(tsk, &times);
thread_group_cputimer(tsk, &times);
ptime = cputime_add(times.utime, times.stime);
if (cputime_le(cval, ptime)) { /* about to fire */
cval = jiffies_to_cputime(1);

95
kernel/posix-cpu-timers.c
View file

@ -230,6 +230,37 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
return 0;
}
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
{
struct sighand_struct *sighand;
struct signal_struct *sig;
struct task_struct *t;
*times = INIT_CPUTIME;
rcu_read_lock();
sighand = rcu_dereference(tsk->sighand);
if (!sighand)
goto out;
sig = tsk->signal;
t = tsk;
do {
times->utime = cputime_add(times->utime, t->utime);
times->stime = cputime_add(times->stime, t->stime);
times->sum_exec_runtime += t->se.sum_exec_runtime;
t = next_thread(t);
} while (t != tsk);
times->utime = cputime_add(times->utime, sig->utime);
times->stime = cputime_add(times->stime, sig->stime);
times->sum_exec_runtime += sig->sum_sched_runtime;
out:
rcu_read_unlock();
}
/*
* Sample a process (thread group) clock for the given group_leader task.
* Must be called with tasklist_lock held for reading.
@ -475,6 +506,29 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
now);
}
/*
* Enable the process wide cpu timer accounting.
*
* serialized using ->sighand->siglock
*/
static void start_process_timers(struct task_struct *tsk)
{
tsk->signal->cputimer.running = 1;
barrier();
}
/*
* Release the process wide timer accounting -- timer stops ticking when
* nobody cares about it.
*
* serialized using ->sighand->siglock
*/
static void stop_process_timers(struct task_struct *tsk)
{
tsk->signal->cputimer.running = 0;
barrier();
}
/*
* Insert the timer on the appropriate list before any timers that
* expire later. This must be called with the tasklist_lock held
@ -495,6 +549,9 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
BUG_ON(!irqs_disabled());
spin_lock(&p->sighand->siglock);
if (!CPUCLOCK_PERTHREAD(timer->it_clock))
start_process_timers(p);
listpos = head;
if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
list_for_each_entry(next, head, entry) {
@ -987,13 +1044,15 @@ static void check_process_timers(struct task_struct *tsk,
sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
list_empty(&timers[CPUCLOCK_VIRT]) &&
cputime_eq(sig->it_virt_expires, cputime_zero) &&
list_empty(&timers[CPUCLOCK_SCHED]))
list_empty(&timers[CPUCLOCK_SCHED])) {
stop_process_timers(tsk);
return;
}
/*
* Collect the current process totals.
*/
thread_group_cputime(tsk, &cputime);
thread_group_cputimer(tsk, &cputime);
utime = cputime.utime;
ptime = cputime_add(utime, cputime.stime);
sum_sched_runtime = cputime.sum_exec_runtime;
@ -1259,7 +1318,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
if (!task_cputime_zero(&sig->cputime_expires)) {
struct task_cputime group_sample;
thread_group_cputime(tsk, &group_sample);
thread_group_cputimer(tsk, &group_sample);
if (task_cputime_expired(&group_sample, &sig->cputime_expires))
return 1;
}
@ -1328,6 +1387,33 @@ void run_posix_cpu_timers(struct task_struct *tsk)
}
}
/*
* Sample a process (thread group) timer for the given group_leader task.
* Must be called with tasklist_lock held for reading.
*/
static int cpu_timer_sample_group(const clockid_t which_clock,
struct task_struct *p,
union cpu_time_count *cpu)
{
struct task_cputime cputime;
thread_group_cputimer(p, &cputime);
switch (CPUCLOCK_WHICH(which_clock)) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
}
/*
* Set one of the process-wide special case CPU timers.
* The tsk->sighand->siglock must be held by the caller.
@ -1341,7 +1427,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
struct list_head *head;
BUG_ON(clock_idx == CPUCLOCK_SCHED);
cpu_clock_sample_group(clock_idx, tsk, &now);
start_process_timers(tsk);
cpu_timer_sample_group(clock_idx, tsk, &now);
if (oldval) {
if (!cputime_eq(*oldval, cputime_zero)) {

45
kernel/sched_stats.h
View file

@ -296,19 +296,21 @@ sched_info_switch(struct task_struct *prev, struct task_struct *next)
static inline void account_group_user_time(struct task_struct *tsk,
cputime_t cputime)
{
struct task_cputime *times;
struct signal_struct *sig;
struct thread_group_cputimer *cputimer;
/* tsk == current, ensure it is safe to use ->signal */
if (unlikely(tsk->exit_state))
return;
sig = tsk->signal;
times = &sig->cputime.totals;
cputimer = &tsk->signal->cputimer;
spin_lock(&times->lock);
times->utime = cputime_add(times->utime, cputime);
spin_unlock(&times->lock);
if (!cputimer->running)
return;
spin_lock(&cputimer->lock);
cputimer->cputime.utime =
cputime_add(cputimer->cputime.utime, cputime);
spin_unlock(&cputimer->lock);
}
/**
@ -324,19 +326,21 @@ static inline void account_group_user_time(struct task_struct *tsk,
static inline void account_group_system_time(struct task_struct *tsk,
cputime_t cputime)
{
struct task_cputime *times;
struct signal_struct *sig;
struct thread_group_cputimer *cputimer;
/* tsk == current, ensure it is safe to use ->signal */
if (unlikely(tsk->exit_state))
return;
sig = tsk->signal;
times = &sig->cputime.totals;
cputimer = &tsk->signal->cputimer;
spin_lock(&times->lock);
times->stime = cputime_add(times->stime, cputime);
spin_unlock(&times->lock);
if (!cputimer->running)
return;
spin_lock(&cputimer->lock);
cputimer->cputime.stime =
cputime_add(cputimer->cputime.stime, cputime);
spin_unlock(&cputimer->lock);
}
/**
@ -352,7 +356,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
static inline void account_group_exec_runtime(struct task_struct *tsk,
unsigned long long ns)
{
struct task_cputime *times;
struct thread_group_cputimer *cputimer;
struct signal_struct *sig;
sig = tsk->signal;
@ -361,9 +365,12 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
if (unlikely(!sig))
return;
times = &sig->cputime.totals;
cputimer = &sig->cputimer;
spin_lock(&times->lock);
times->sum_exec_runtime += ns;
spin_unlock(&times->lock);
if (!cputimer->running)
return;
spin_lock(&cputimer->lock);
cputimer->cputime.sum_exec_runtime += ns;
spin_unlock(&cputimer->lock);
}