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Posix timers: limit number of timers firing at once

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Bursty timers aren't good for anybody, very much including latency for
other programs when we trigger lots of timers in interrupt context.  So
set a random limit, after which we'll handle the rest on the next timer
tick.

Noted by Oleg Nesterov <oleg@tv-sign.ru>

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Linus Torvalds 2005-10-23 10:02:50 -07:00
parent d475f3f47a
commit e80eda94d3
1 changed files with 14 additions and 6 deletions
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20
kernel/posix-cpu-timers.c
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@ -961,14 +961,16 @@ void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
static void check_thread_timers(struct task_struct *tsk, static void check_thread_timers(struct task_struct *tsk,
struct list_head *firing) struct list_head *firing)
{ {
int maxfire;
struct list_head *timers = tsk->cpu_timers; struct list_head *timers = tsk->cpu_timers;
maxfire = 20;
tsk->it_prof_expires = cputime_zero; tsk->it_prof_expires = cputime_zero;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (cputime_lt(prof_ticks(tsk), t->expires.cpu)) { if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
tsk->it_prof_expires = t->expires.cpu; tsk->it_prof_expires = t->expires.cpu;
break; break;
} }
@ -977,12 +979,13 @@ static void check_thread_timers(struct task_struct *tsk,
} }
++timers; ++timers;
maxfire = 20;
tsk->it_virt_expires = cputime_zero; tsk->it_virt_expires = cputime_zero;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (cputime_lt(virt_ticks(tsk), t->expires.cpu)) { if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
tsk->it_virt_expires = t->expires.cpu; tsk->it_virt_expires = t->expires.cpu;
break; break;
} }
@ -991,12 +994,13 @@ static void check_thread_timers(struct task_struct *tsk,
} }
++timers; ++timers;
maxfire = 20;
tsk->it_sched_expires = 0; tsk->it_sched_expires = 0;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (tsk->sched_time < t->expires.sched) { if (!--maxfire || tsk->sched_time < t->expires.sched) {
tsk->it_sched_expires = t->expires.sched; tsk->it_sched_expires = t->expires.sched;
break; break;
} }
@ -1013,6 +1017,7 @@ static void check_thread_timers(struct task_struct *tsk,
static void check_process_timers(struct task_struct *tsk, static void check_process_timers(struct task_struct *tsk,
struct list_head *firing) struct list_head *firing)
{ {
int maxfire;
struct signal_struct *const sig = tsk->signal; struct signal_struct *const sig = tsk->signal;
cputime_t utime, stime, ptime, virt_expires, prof_expires; cputime_t utime, stime, ptime, virt_expires, prof_expires;
unsigned long long sched_time, sched_expires; unsigned long long sched_time, sched_expires;
@ -1045,12 +1050,13 @@ static void check_process_timers(struct task_struct *tsk,
} while (t != tsk); } while (t != tsk);
ptime = cputime_add(utime, stime); ptime = cputime_add(utime, stime);
maxfire = 20;
prof_expires = cputime_zero; prof_expires = cputime_zero;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (cputime_lt(ptime, t->expires.cpu)) { if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
prof_expires = t->expires.cpu; prof_expires = t->expires.cpu;
break; break;
} }
@ -1059,12 +1065,13 @@ static void check_process_timers(struct task_struct *tsk,
} }
++timers; ++timers;
maxfire = 20;
virt_expires = cputime_zero; virt_expires = cputime_zero;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (cputime_lt(utime, t->expires.cpu)) { if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
virt_expires = t->expires.cpu; virt_expires = t->expires.cpu;
break; break;
} }
@ -1073,12 +1080,13 @@ static void check_process_timers(struct task_struct *tsk,
} }
++timers; ++timers;
maxfire = 20;
sched_expires = 0; sched_expires = 0;
while (!list_empty(timers)) { while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next, struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list, struct cpu_timer_list,
entry); entry);
if (sched_time < t->expires.sched) { if (!--maxfire || sched_time < t->expires.sched) {
sched_expires = t->expires.sched; sched_expires = t->expires.sched;
break; break;
} }