The patch titled cpu-timers: optimize run_posix_cpu_timers() has been added to the -mm tree. Its filename is cpu-timers-optimize-run_posix_cpu_timers.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: cpu-timers: optimize run_posix_cpu_timers() From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> We can optimize and simplify things taking into account signal->cputimer is always running when we have configured any process wide cpu timer. In check_process_timers(), we don't have to check if new updated value of signal->cputime_expires is smaller, since we maintain new first expiration time ({prof,virt,sched}_expires) in code flow and all other writes to expiration cache are protected by sighand->siglock . Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx> Cc: Balbir Singh <balbir@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/posix-cpu-timers.c | 80 +++++++++++++----------------------- 1 file changed, 29 insertions(+), 51 deletions(-) diff -puN kernel/posix-cpu-timers.c~cpu-timers-optimize-run_posix_cpu_timers kernel/posix-cpu-timers.c --- a/kernel/posix-cpu-timers.c~cpu-timers-optimize-run_posix_cpu_timers +++ a/kernel/posix-cpu-timers.c @@ -1000,16 +1000,9 @@ static void stop_process_timers(struct s struct thread_group_cputimer *cputimer = &sig->cputimer; unsigned long flags; - if (!cputimer->running) - return; - spin_lock_irqsave(&cputimer->lock, flags); cputimer->running = 0; spin_unlock_irqrestore(&cputimer->lock, flags); - - sig->cputime_expires.prof_exp = cputime_zero; - sig->cputime_expires.virt_exp = cputime_zero; - sig->cputime_expires.sched_exp = 0; } static u32 onecputick; @@ -1046,6 +1039,23 @@ static void check_cpu_itimer(struct task } } +/** + * task_cputime_zero - Check a task_cputime struct for all zero fields. + * + * @cputime: The struct to compare. + * + * Checks @cputime to see if all fields are zero. Returns true if all fields + * are zero, false if any field is nonzero. + */ +static inline int task_cputime_zero(const struct task_cputime *cputime) +{ + if (cputime_eq(cputime->utime, cputime_zero) && + cputime_eq(cputime->stime, cputime_zero) && + cputime->sum_exec_runtime == 0) + return 1; + return 0; +} + /* * Check for any per-thread CPU timers that have fired and move them * off the tsk->*_timers list onto the firing list. Per-thread timers @@ -1062,19 +1072,6 @@ static void check_process_timers(struct struct task_cputime cputime; /* - * Don't sample the current process CPU clocks if there are no timers. - */ - if (list_empty(&timers[CPUCLOCK_PROF]) && - cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) && - sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY && - list_empty(&timers[CPUCLOCK_VIRT]) && - cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) && - list_empty(&timers[CPUCLOCK_SCHED])) { - stop_process_timers(sig); - return; - } - - /* * Collect the current process totals. */ thread_group_cputimer(tsk, &cputime); @@ -1161,18 +1158,11 @@ static void check_process_timers(struct } } - if (!cputime_eq(prof_expires, cputime_zero) && - (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) || - cputime_gt(sig->cputime_expires.prof_exp, prof_expires))) - sig->cputime_expires.prof_exp = prof_expires; - if (!cputime_eq(virt_expires, cputime_zero) && - (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) || - cputime_gt(sig->cputime_expires.virt_exp, virt_expires))) - sig->cputime_expires.virt_exp = virt_expires; - if (sched_expires != 0 && - (sig->cputime_expires.sched_exp == 0 || - sig->cputime_expires.sched_exp > sched_expires)) - sig->cputime_expires.sched_exp = sched_expires; + sig->cputime_expires.prof_exp = prof_expires; + sig->cputime_expires.virt_exp = virt_expires; + sig->cputime_expires.sched_exp = sched_expires; + if (task_cputime_zero(&sig->cputime_expires)) + stop_process_timers(sig); } /* @@ -1245,23 +1235,6 @@ out: } /** - * task_cputime_zero - Check a task_cputime struct for all zero fields. - * - * @cputime: The struct to compare. - * - * Checks @cputime to see if all fields are zero. Returns true if all fields - * are zero, false if any field is nonzero. - */ -static inline int task_cputime_zero(const struct task_cputime *cputime) -{ - if (cputime_eq(cputime->utime, cputime_zero) && - cputime_eq(cputime->stime, cputime_zero) && - cputime->sum_exec_runtime == 0) - return 1; - return 0; -} - -/** * task_cputime_expired - Compare two task_cputime entities. * * @sample: The task_cputime structure to be checked for expiration. @@ -1317,7 +1290,7 @@ static inline int fastpath_timer_check(s } sig = tsk->signal; - if (!task_cputime_zero(&sig->cputime_expires)) { + if (sig->cputimer.running) { struct task_cputime group_sample; thread_group_cputimer(tsk, &group_sample); @@ -1354,7 +1327,12 @@ void run_posix_cpu_timers(struct task_st * put them on the firing list. */ check_thread_timers(tsk, &firing); - check_process_timers(tsk, &firing); + /* + * If there are any active process wide timers (POSIX 1.b, itimers, + * RLIMIT_CPU) cputimer must be running. + */ + if (tsk->signal->cputimer.running) + check_process_timers(tsk, &firing); /* * We must release these locks before taking any timer's lock. _ Patches currently in -mm which might be from sgruszka@xxxxxxxxxx are posix-cpu-timers-reset-expire-cache-when-no-timer-is-running.patch cpu-timers-simplify-rlimit_cpu-handling.patch cpu-timers-cleanup-arm_timer.patch cpu-timers-return-correct-previous-timer-reload-value.patch cpu-timers-change-sigev_none-timer-implementation.patch cpu-timers-assure-to-not-iterate-over-all-threads-in-fastpath_timer_check.patch cpu-timers-optimize-run_posix_cpu_timers.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