The patch titled
itimers: fix periodic tics precision
has been removed from the -mm tree. Its filename was
itimers-fix-periodic-tics-precision.patch
This patch was dropped because an updated version will be merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: itimers: fix periodic tics precision
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Measure interval of tics generated by ITIMER_VIRT and ITIMER_PROF using
ktime instead of cputime. Calculate error between requested interval and
current one, take it into account when scheduling next tick.
This patch introduce possibility where time between two consecutive tics
is smaller then requested interval, it preserve however dependency that n
tick is generated not earlier than n*interval time - counting from the
beginning of periodic signal generation.
Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: john stultz <johnstul@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 3 ++-
kernel/fork.c | 6 ++++--
kernel/itimer.c | 23 +++++++++++++----------
kernel/posix-cpu-timers.c | 24 +++++++++++++++++++++---
4 files changed, 40 insertions(+), 16 deletions(-)
diff -puN include/linux/sched.h~itimers-fix-periodic-tics-precision include/linux/sched.h
--- a/include/linux/sched.h~itimers-fix-periodic-tics-precision
+++ a/include/linux/sched.h
@@ -457,7 +457,8 @@ struct pacct_struct {
struct cpu_itimer {
cputime_t expires;
- cputime_t incr;
+ ktime_t incr;
+ u32 err_ns;
};
/**
diff -puN kernel/fork.c~itimers-fix-periodic-tics-precision kernel/fork.c
--- a/kernel/fork.c~itimers-fix-periodic-tics-precision
+++ a/kernel/fork.c
@@ -790,9 +790,11 @@ static void posix_cpu_timers_init_group(
/* Expiration times and increments. */
sig->it[0].expires = cputime_zero;
- sig->it[0].incr = cputime_zero;
+ sig->it[0].incr = ktime_set(0, 0);
+ sig->it[0].err_ns = 0;
sig->it[1].expires = cputime_zero;
- sig->it[1].incr = cputime_zero;
+ sig->it[1].incr = ktime_set(0, 0);
+ sig->it[1].err_ns = 0;
/* Cached expiration times. */
sig->cputime_expires.prof_exp = cputime_zero;
diff -puN kernel/itimer.c~itimers-fix-periodic-tics-precision kernel/itimer.c
--- a/kernel/itimer.c~itimers-fix-periodic-tics-precision
+++ a/kernel/itimer.c
@@ -42,15 +42,16 @@ static struct timeval itimer_get_remtime
}
static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
- struct itimerval *value)
+ struct itimerval *const value)
{
- cputime_t cval, cinterval;
+ cputime_t cval;
+ ktime_t kt_cinterval;
struct cpu_itimer *it = &tsk->signal->it[clock_id];
spin_lock_irq(&tsk->sighand->siglock);
cval = it->expires;
- cinterval = it->incr;
+ kt_cinterval = it->incr;
if (!cputime_eq(cval, cputime_zero)) {
struct task_cputime cputime;
cputime_t t;
@@ -77,7 +78,7 @@ static void get_cpu_itimer(struct task_s
spin_unlock_irq(&tsk->sighand->siglock);
cputime_to_timeval(cval, &value->it_value);
- cputime_to_timeval(cinterval, &value->it_interval);
+ value->it_interval = ktime_to_timeval(kt_cinterval);
}
int do_getitimer(int which, struct itimerval *value)
@@ -133,18 +134,20 @@ enum hrtimer_restart it_real_fn(struct h
}
static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
- struct itimerval *value, struct itimerval *ovalue)
+ const struct itimerval *const value,
+ struct itimerval *const ovalue)
{
- cputime_t cval, cinterval, nval, ninterval;
+ cputime_t cval, nval;
+ ktime_t kt_cinterval, kt_ninterval;
struct cpu_itimer *it = &tsk->signal->it[clock_id];
nval = timeval_to_cputime(&value->it_value);
- ninterval = timeval_to_cputime(&value->it_interval);
+ kt_ninterval = timeval_to_ktime(value->it_interval);
spin_lock_irq(&tsk->sighand->siglock);
cval = it->expires;
- cinterval = it->incr;
+ kt_cinterval = it->incr;
if (!cputime_eq(cval, cputime_zero) ||
!cputime_eq(nval, cputime_zero)) {
if (cputime_gt(nval, cputime_zero))
@@ -152,13 +155,13 @@ static void set_cpu_itimer(struct task_s
set_process_cpu_timer(tsk, clock_id, &nval, &cval);
}
it->expires = nval;
- it->incr = ninterval;
+ it->incr = kt_ninterval;
spin_unlock_irq(&tsk->sighand->siglock);
if (ovalue) {
cputime_to_timeval(cval, &ovalue->it_value);
- cputime_to_timeval(cinterval, &ovalue->it_interval);
+ ovalue->it_interval = ktime_to_timeval(kt_cinterval);
}
}
diff -puN kernel/posix-cpu-timers.c~itimers-fix-periodic-tics-precision kernel/posix-cpu-timers.c
--- a/kernel/posix-cpu-timers.c~itimers-fix-periodic-tics-precision
+++ a/kernel/posix-cpu-timers.c
@@ -1080,9 +1080,27 @@ static void check_cpu_itimer(struct task
return;
if (cputime_ge(cur_time, it->expires)) {
- it->expires = it->incr;
- if (!cputime_eq(it->expires, cputime_zero)) {
- it->expires = cputime_add(it->expires, cur_time);
+ if (it->incr.tv64 != 0) {
+ ktime_t incr, real_incr, diff;
+ cputime_t cpu_incr;
+ struct timespec ts_incr, ts_real_incr;
+
+ incr = ktime_sub_ns(it->incr, it->err_ns);
+ if (unlikely(incr.tv64 <= 0))
+ incr = ktime_set(0, 1);
+
+ ts_incr = ktime_to_timespec(incr);
+ cpu_incr = timespec_to_cputime(&ts_incr);
+
+ cputime_to_timespec(cpu_incr, &ts_real_incr);
+ real_incr = timespec_to_ktime(ts_real_incr);
+
+ diff = ktime_sub(real_incr, incr);
+ it->err_ns = ktime_to_ns(diff);
+ it->expires = cputime_add(it->expires, cpu_incr);
+ } else {
+ it->expires = cputime_zero;
+ it->err_ns = 0;
}
__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
_
Patches currently in -mm which might be from sgruszka@xxxxxxxxxx are
linux-next.patch
itimers-fix-periodic-tics-precision.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
