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authorJason Low <jason.low2@hp.com>2015-10-14 12:07:54 -0700
committerThomas Gleixner <tglx@linutronix.de>2015-10-15 11:23:41 +0200
commit934715a191e4be0c602d39455a7a74316f274d60 (patch)
tree30b902d66d43fc5079831f81b722399d04286c99 /kernel/time
parent7c177d994eb9637302b79e80d331f48dfbe26368 (diff)
downloadlinux-934715a191e4be0c602d39455a7a74316f274d60.tar.bz2
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.low2@hp.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: George Spelvin <linux@horizon.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1444849677-29330-3-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/posix-cpu-timers.c22
1 files changed, 16 insertions, 6 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index aa4b6f4f3b5e..6f6e252ec761 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.