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posix-cpu-timers: Get rid of 64bit divisions 

Instead of dividing A to match the units of B it's more efficient to
multiply B to match the units of A.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192922.458286860@linutronix.de
This commit is contained in:
Thomas Gleixner 2019-08-21 21:09:21 +02:00
parent 1cd07c0b94
commit 8ea1de90a5
1 changed files with 14 additions and 10 deletions
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24
kernel/time/posix-cpu-timers.c
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@ -798,10 +798,11 @@ static void check_thread_timers(struct task_struct *tsk,
*/
soft = task_rlimit(tsk, RLIMIT_RTTIME);
if (soft != RLIM_INFINITY) {
/* Task RT timeout is accounted in jiffies. RTTIME is usec */
unsigned long rtim = tsk->rt.timeout * (USEC_PER_SEC / HZ);
unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
if (hard != RLIM_INFINITY &&
tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
if (hard != RLIM_INFINITY && rtim >= hard) {
/*
* At the hard limit, we just die.
* No need to calculate anything else now.
@ -813,7 +814,7 @@ static void check_thread_timers(struct task_struct *tsk,
__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
return;
}
if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
if (rtim >= soft) {
/*
* At the soft limit, send a SIGXCPU every second.
*/
@ -910,11 +911,13 @@ static void check_process_timers(struct task_struct *tsk,
soft = task_rlimit(tsk, RLIMIT_CPU);
if (soft != RLIM_INFINITY) {
u64 softns, ptime = samples[CPUCLOCK_PROF];
/* RLIMIT_CPU is in seconds. Samples are nanoseconds */
unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
u64 ptime = samples[CPUCLOCK_PROF];
u64 softns = (u64)soft * NSEC_PER_SEC;
u64 hardns = (u64)hard * NSEC_PER_SEC;
if (hard != RLIM_INFINITY && psecs >= hard) {
if (hard != RLIM_INFINITY && ptime >= hardns) {
/*
* At the hard limit, we just die.
* No need to calculate anything else now.
@ -926,7 +929,7 @@ static void check_process_timers(struct task_struct *tsk,
__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
return;
}
if (psecs >= soft) {
if (ptime >= softns) {
/*
* At the soft limit, send a SIGXCPU every second.
*/
@ -936,11 +939,12 @@ static void check_process_timers(struct task_struct *tsk,
}
__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
if (soft < hard) {
soft++;
sig->rlim[RLIMIT_CPU].rlim_cur = soft;
sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
softns += NSEC_PER_SEC;
}
}
softns = soft * NSEC_PER_SEC;
/* Update the expiry cache */
if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
pct->bases[CPUCLOCK_PROF].nextevt = softns;
}