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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-05 15:30:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-05 15:30:49 -0800 |
| commit | 897e81bea1fcfcd2c5cdb720c9efdb25da9ff374 (patch) | |
| tree | 92cf33ed2c35c1ece633f09365702f1c8e24d415 /kernel/time.c | |
| parent | c3fa27d1367fac63ac8533d6f20ea851d0d70a10 (diff) | |
| parent | 0cf55e1ec08bb5a22e068309e2d8ba1180ab4239 (diff) | |
| download | kernel-crypto-897e81bea1fcfcd2c5cdb720c9efdb25da9ff374.tar.gz kernel-crypto-897e81bea1fcfcd2c5cdb720c9efdb25da9ff374.tar.xz kernel-crypto-897e81bea1fcfcd2c5cdb720c9efdb25da9ff374.zip | |
Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (35 commits)
sched, cputime: Introduce thread_group_times()
sched, cputime: Cleanups related to task_times()
Revert "sched, x86: Optimize branch hint in __switch_to()"
sched: Fix isolcpus boot option
sched: Revert 498657a478c60be092208422fefa9c7b248729c2
sched, time: Define nsecs_to_jiffies()
sched: Remove task_{u,s,g}time()
sched: Introduce task_times() to replace task_{u,s}time() pair
sched: Limit the number of scheduler debug messages
sched.c: Call debug_show_all_locks() when dumping all tasks
sched, x86: Optimize branch hint in __switch_to()
sched: Optimize branch hint in context_switch()
sched: Optimize branch hint in pick_next_task_fair()
sched_feat_write(): Update ppos instead of file->f_pos
sched: Sched_rt_periodic_timer vs cpu hotplug
sched, kvm: Fix race condition involving sched_in_preempt_notifers
sched: More generic WAKE_AFFINE vs select_idle_sibling()
sched: Cleanup select_task_rq_fair()
sched: Fix granularity of task_u/stime()
sched: Fix/add missing update_rq_clock() calls
...
Diffstat (limited to 'kernel/time.c')
| -rw-r--r-- | kernel/time.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/time.c b/kernel/time.c index 2e2e469a7fe..804798005d1 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -662,6 +662,36 @@ u64 nsec_to_clock_t(u64 x) #endif } +/** + * nsecs_to_jiffies - Convert nsecs in u64 to jiffies + * + * @n: nsecs in u64 + * + * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. + * And this doesn't return MAX_JIFFY_OFFSET since this function is designed + * for scheduler, not for use in device drivers to calculate timeout value. + * + * note: + * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) + * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years + */ +unsigned long nsecs_to_jiffies(u64 n) +{ +#if (NSEC_PER_SEC % HZ) == 0 + /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ + return div_u64(n, NSEC_PER_SEC / HZ); +#elif (HZ % 512) == 0 + /* overflow after 292 years if HZ = 1024 */ + return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); +#else + /* + * Generic case - optimized for cases where HZ is a multiple of 3. + * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. + */ + return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); +#endif +} + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { |