| Date | Mon, 19 Aug 2019 16:32:20 +0200 | From | Thomas Gleixner <> | Subject | [patch 39/44] 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> --- kernel/time/posix-cpu-timers.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
--- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -791,10 +791,11 @@ static void check_thread_timers(struct t */ 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. @@ -806,7 +807,7 @@ static void check_thread_timers(struct t __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. */ @@ -901,11 +902,13 @@ static void check_process_timers(struct soft = task_rlimit(tsk, RLIMIT_CPU); if (soft != RLIM_INFINITY) { + /* RLIMIT_CPU is in seconds. Samples are nanoseconds */ unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU); - u64 softns, ptime = samples[CPUCLOCK_PROF]; - 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. @@ -917,7 +920,7 @@ static void check_process_timers(struct __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. */ @@ -931,7 +934,8 @@ static void check_process_timers(struct sig->rlim[RLIMIT_CPU].rlim_cur = soft; } } - softns = soft * NSEC_PER_SEC; + + /* Update the expiry cache */ if (softns < exp[CPUCLOCK_PROF]) exp[CPUCLOCK_PROF] = softns; }
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