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authorLinus Torvalds <torvalds@g5.osdl.org>2005-10-23 17:02:50 (GMT)
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-23 17:02:50 (GMT)
commite80eda94d3eaf1d12cfc97878eff77cd679dabc9 (patch)
tree38ab17e7b9839297708a6982d661c3725d181c3a /kernel
parentd475f3f47a0427dfee483cecf9a7e9109e991423 (diff)
downloadlinux-e80eda94d3eaf1d12cfc97878eff77cd679dabc9.tar.xz
Posix timers: limit number of timers firing at once
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-cpu-timers.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 7a51a55..d30b304 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -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,
struct list_head *firing)
{
+ int maxfire;
struct list_head *timers = tsk->cpu_timers;
+ maxfire = 20;
tsk->it_prof_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
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;
break;
}
@@ -977,12 +979,13 @@ static void check_thread_timers(struct task_struct *tsk,
}
++timers;
+ maxfire = 20;
tsk->it_virt_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
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;
break;
}
@@ -991,12 +994,13 @@ static void check_thread_timers(struct task_struct *tsk,
}
++timers;
+ maxfire = 20;
tsk->it_sched_expires = 0;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
entry);
- if (tsk->sched_time < t->expires.sched) {
+ if (!--maxfire || tsk->sched_time < t->expires.sched) {
tsk->it_sched_expires = t->expires.sched;
break;
}
@@ -1013,6 +1017,7 @@ static void check_thread_timers(struct task_struct *tsk,
static void check_process_timers(struct task_struct *tsk,
struct list_head *firing)
{
+ int maxfire;
struct signal_struct *const sig = tsk->signal;
cputime_t utime, stime, ptime, virt_expires, prof_expires;
unsigned long long sched_time, sched_expires;
@@ -1045,12 +1050,13 @@ static void check_process_timers(struct task_struct *tsk,
} while (t != tsk);
ptime = cputime_add(utime, stime);
+ maxfire = 20;
prof_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
entry);
- if (cputime_lt(ptime, t->expires.cpu)) {
+ if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
prof_expires = t->expires.cpu;
break;
}
@@ -1059,12 +1065,13 @@ static void check_process_timers(struct task_struct *tsk,
}
++timers;
+ maxfire = 20;
virt_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
entry);
- if (cputime_lt(utime, t->expires.cpu)) {
+ if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
virt_expires = t->expires.cpu;
break;
}
@@ -1073,12 +1080,13 @@ static void check_process_timers(struct task_struct *tsk,
}
++timers;
+ maxfire = 20;
sched_expires = 0;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_entry(timers->next,
struct cpu_timer_list,
entry);
- if (sched_time < t->expires.sched) {
+ if (!--maxfire || sched_time < t->expires.sched) {
sched_expires = t->expires.sched;
break;
}