Commit-ID: 934715a191e4be0c602d39455a7a74316f274d60 Gitweb: http://git.kernel.org/tip/934715a191e4be0c602d39455a7a74316f274d60 Author: Jason Low <jason.l...@hp.com> AuthorDate: Wed, 14 Oct 2015 12:07:54 -0700 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Thu, 15 Oct 2015 11:23:41 +0200
posix_cpu_timer: Check thread timers only when there are active thread timers The fastpath_timer_check() contains logic to check for if any timers are set by checking if !task_cputime_zero(). Similarly, we can do this before calling check_thread_timers(). In the case where there are only process-wide timers, this will skip all of the computations for per-thread timers when there are no per-thread timers. As suggested by George, we can put the task_cputime_zero() check in check_thread_timers(), since that is more of an optization to the function. Similarly, we move the existing check of cputimer->running to check_process_timers(). Signed-off-by: Jason Low <jason.l...@hp.com> Reviewed-by: Oleg Nesterov <o...@redhat.com> Reviewed-by: George Spelvin <li...@horizon.com> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: Davidlohr Bueso <d...@stgolabs.net> Cc: Steven Rostedt <rost...@goodmis.org> Cc: hideaki.kim...@hpe.com Cc: terry.r...@hpe.com Cc: scott.nor...@hpe.com Cc: Peter Zijlstra <pet...@infradead.org> Link: http://lkml.kernel.org/r/1444849677-29330-3-git-send-email-jason.l...@hp.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- kernel/time/posix-cpu-timers.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index aa4b6f4..6f6e252 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -864,6 +864,13 @@ static void check_thread_timers(struct task_struct *tsk, unsigned long long expires; unsigned long soft; + /* + * If cputime_expires is zero, then there are no active + * per thread CPU timers. + */ + if (task_cputime_zero(&tsk->cputime_expires)) + return; + expires = check_timers_list(timers, firing, prof_ticks(tsk)); tsk_expires->prof_exp = expires_to_cputime(expires); @@ -962,6 +969,13 @@ static void check_process_timers(struct task_struct *tsk, unsigned long soft; /* + * If cputimer is not running, then there are no active + * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU). + */ + if (!READ_ONCE(tsk->signal->cputimer.running)) + return; + + /* * Collect the current process totals. */ thread_group_cputimer(tsk, &cputime); @@ -1169,12 +1183,8 @@ void run_posix_cpu_timers(struct task_struct *tsk) * put them on the firing list. */ check_thread_timers(tsk, &firing); - /* - * If there are any active process wide timers (POSIX 1.b, itimers, - * RLIMIT_CPU) cputimer must be running. - */ - if (READ_ONCE(tsk->signal->cputimer.running)) - check_process_timers(tsk, &firing); + + check_process_timers(tsk, &firing); /* * We must release these locks before taking any timer's lock. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
