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john stultz da15cfdae0 time: Introduce CLOCK_REALTIME_COARSE 
After talking with some application writers who want very fast, but not
fine-grained timestamps, I decided to try to implement new clock_ids
to clock_gettime(): CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE
which returns the time at the last tick. This is very fast as we don't
have to access any hardware (which can be very painful if you're using
something like the acpi_pm clocksource), and we can even use the vdso
clock_gettime() method to avoid the syscall. The only trade off is you
only get low-res tick grained time resolution.

This isn't a new idea, I know Ingo has a patch in the -rt tree that made
the vsyscall gettimeofday() return coarse grained time when the
vsyscall64 sysctrl was set to 2. However this affects all applications
on a system.

With this method, applications can choose the proper speed/granularity
trade-off for themselves.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: nikolag@ca.ibm.com
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: arjan@infradead.org
Cc: jonathan@jonmasters.org
LKML-Reference: <1250734414.6897.5.camel@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-08-21 21:43:46 +02:00
..
gcov gcov: enable GCOV_PROFILE_ALL for x86_64 2009-06-18 13:03:58 -07:00
irq genirq: prevent wakeup of freed irq thread 2009-08-13 23:09:27 +02:00
power headers: smp_lock.h redux 2009-07-12 12:22:34 -07:00
time time: Introduce CLOCK_REALTIME_COARSE 2009-08-21 21:43:46 +02:00
trace Remove double removal of blktrace directory 2009-08-12 18:50:08 +02:00
.gitignore
acct.c bsdacct: fix access to invalid filp in acct_on() 2009-06-30 18:56:00 -07:00
async.c async: Fix lack of boot-time console due to insufficient synchronization 2009-06-08 12:31:53 -07:00
audit.c Fix rule eviction order for AUDIT_DIR 2009-06-24 00:02:38 -04:00
audit.h Fix rule eviction order for AUDIT_DIR 2009-06-24 00:02:38 -04:00
audit_tree.c Fix rule eviction order for AUDIT_DIR 2009-06-24 00:02:38 -04:00
audit_watch.c Audit: clean up all op= output to include string quoting 2009-06-24 00:00:52 -04:00
auditfilter.c Audit: clean up all op= output to include string quoting 2009-06-24 00:00:52 -04:00
auditsc.c Fix rule eviction order for AUDIT_DIR 2009-06-24 00:02:38 -04:00
backtracetest.c
bounds.c
capability.c
cgroup.c cgroup avoid permanent sleep at rmdir 2009-07-29 19:10:35 -07:00
cgroup_debug.c debug cgroup: remove unneeded cgroup_lock 2009-04-02 19:04:54 -07:00
cgroup_freezer.c
compat.c signals: implement sys_rt_tgsigqueueinfo 2009-04-30 19:24:24 +02:00
configs.c
cpu.c mm/init: cpu_hotplug_init() must be initialized before SLAB 2009-06-22 21:18:12 -07:00
cpuset.c cpuset,mm: update tasks' mems_allowed in time 2009-06-16 19:47:31 -07:00
cred-internals.h
cred.c CRED: Rename cred_exec_mutex to reflect that it's a guard against ptrace 2009-05-11 08:15:36 +10:00
delayacct.c
dma-coherent.c
dma.c
exec_domain.c Get rid of indirect include of fs_struct.h 2009-03-31 23:00:27 -04:00
exit.c headers: mnt_namespace.h redux 2009-07-08 09:31:56 -07:00
extable.c Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-04-05 11:04:19 -07:00
fork.c execve: must clear current->clear_child_tid 2009-08-07 10:39:56 -07:00
freezer.c sched: fix nr_uninterruptible accounting of frozen tasks really 2009-07-18 14:19:53 +02:00
futex.c futex: Fix handling of bad requeue syscall pairing 2009-08-10 20:38:11 +02:00
futex_compat.c futex: Fix compat_futex to be same as futex for REQUEUE_PI 2009-08-10 15:41:12 +02:00
groups.c groups: move code to kernel/groups.c 2009-06-16 19:47:48 -07:00
hrtimer.c Merge branch 'linus' into timers/core 2009-08-14 15:59:30 +02:00
hung_task.c
itimer.c
kallsyms.c kernel/kallsyms.c: replace deprecated __initcall with device_initcall and fix whitespace 2009-06-09 22:37:52 +02:00
Kconfig.freezer
Kconfig.hz
Kconfig.preempt
kexec.c kexec: fix omitting offset in extended crashkernel syntax 2009-07-29 19:10:34 -07:00
kfifo.c kernel/kfifo.c: replace conditional test with is_power_of_2() 2009-06-16 19:47:47 -07:00
kgdb.c sysrq, intel_fb: fix sysrq g collision 2009-05-15 07:56:24 -05:00
kmod.c headers: mnt_namespace.h redux 2009-07-08 09:31:56 -07:00
kprobes.c kprobes: Use kernel_text_address() for checking probe address 2009-07-30 16:44:06 -07:00
ksysfs.c
kthread.c update the comment in kthread_stop() 2009-07-27 12:15:46 -07:00
latencytop.c
lockdep.c Merge branch 'linus' into tracing/core 2009-05-07 11:17:34 +02:00
lockdep_internals.h lockdep: increase MAX_LOCKDEP_ENTRIES and MAX_LOCKDEP_CHAINS 2009-05-12 19:59:52 +02:00
lockdep_proc.c lockdep: Fix file mode of lock_stat 2009-08-07 11:58:38 +02:00
lockdep_states.h
Makefile Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-28 11:05:04 -07:00
marker.c
module.c module: use MODULE_SYMBOL_PREFIX with module_layout 2009-07-27 12:15:45 -07:00
mutex-debug.c
mutex-debug.h
mutex.c Merge branch 'linus' into perfcounters/core 2009-06-11 17:55:42 +02:00
mutex.h
notifier.c
ns_cgroup.c cgroups: relax ns_can_attach checks to allow attaching to grandchild cgroups 2009-04-02 19:04:53 -07:00
nsproxy.c nsproxy: extract create_nsproxy() 2009-06-18 13:03:56 -07:00
panic.c trace: stop tracer in oops_enter() 2009-07-24 15:30:45 -04:00
params.c module_param: allow 'bool' module_params to be bool, not just int. 2009-06-12 21:46:58 +09:30
perf_counter.c perf_counter: Report the cloning task as parent on perf_counter_fork() 2009-08-13 16:17:15 +02:00
pid.c kmemleak: Remove alloc_bootmem annotations introduced in the past 2009-07-09 17:07:02 +01:00
pid_namespace.c pidns: rewrite copy_pid_ns() 2009-06-18 13:03:55 -07:00
pm_qos_params.c
posix-cpu-timers.c posix_cpu_timers_exit_group(): Do not use thread_group_cputimer() 2009-08-08 18:30:25 +02:00
posix-timers.c time: Introduce CLOCK_REALTIME_COARSE 2009-08-21 21:43:46 +02:00
printk.c printk: Add KERN_DEFAULT printk log-level 2009-06-16 11:02:28 -07:00
profile.c profile: suppress warning about large allocations when profile=1 is specified 2009-07-29 19:10:36 -07:00
ptrace.c cred_guard_mutex: do not return -EINTR to user-space 2009-07-06 13:57:04 -07:00
rcuclassic.c kmemtrace, rcu: fix linux/rcutree.h and linux/rcuclassic.h dependencies 2009-04-03 12:23:02 +02:00
rcupdate.c RCU: Don't try and predeclare inline funcs as it upsets some versions of gcc 2009-04-15 13:55:14 -07:00
rcupreempt.c rcu: rcu_sched_grace_period(): kill the bogus flush_signals() 2009-05-05 20:28:05 +02:00
rcupreempt_trace.c
rcutorture.c cpumask: convert rcutorture.c 2009-03-30 22:05:16 +10:30
rcutree.c rcu: Mark Hierarchical RCU no longer experimental 2009-06-24 15:02:48 +02:00
rcutree.h kmemtrace, rcu: fix rcu_tree_trace.c data structure dependencies 2009-04-03 12:23:03 +02:00
rcutree_trace.c rcu: Add __rcu_pending tracing to hierarchical RCU 2009-04-14 11:33:43 +02:00
relay.c Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-04-05 11:04:19 -07:00
res_counter.c memcg: add interface to reset limits 2009-06-18 13:03:48 -07:00
resource.c kernel/resource.c: fix sign extension in reserve_setup() 2009-06-30 18:56:00 -07:00
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c rtmutex: Avoid deadlock in rt_mutex_start_proxy_lock() 2009-08-06 05:50:21 +02:00
rtmutex.h
rtmutex_common.h rt_mutex: add proxy lock routines 2009-04-06 11:14:02 +02:00
rwsem.c
sched.c sched: fix load average accounting vs. cpu hotplug 2009-07-18 14:19:52 +02:00
sched_clock.c sched: Fix fallback sched_clock()'s offset when using jiffies 2009-05-09 10:08:19 +02:00
sched_cpupri.c sched: Fix race in cpupri introduced by cpumask_var changes 2009-08-02 14:23:29 +02:00
sched_cpupri.h cpumask: remove cpumask_t from core 2009-03-30 22:05:17 +10:30
sched_debug.c sched: Hide runqueues from direct refer at source code level 2009-06-17 18:29:42 +02:00
sched_fair.c sched: Fix latencytop and sleep profiling vs group scheduling 2009-08-02 14:10:12 +02:00
sched_features.h Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-03-30 17:17:35 -07:00
sched_idletask.c sched, timers: move calc_load() to scheduler 2009-05-15 15:32:45 +02:00
sched_rt.c sched_rt: Fix overload bug on rt group scheduling 2009-07-10 10:43:29 +02:00
sched_stats.h sched: remove unused fields from struct rq 2009-03-24 23:16:51 +01:00
seccomp.c x86-64: seccomp: fix 32/64 syscall hole 2009-03-02 15:41:30 -08:00
semaphore.c
signal.c do_sigaltstack: small cleanups 2009-08-01 11:18:56 -07:00
slow-work.c slow-work: use round_jiffies() for thread pool's cull and OOM timers 2009-06-16 19:47:49 -07:00
smp.c generic-ipi: fix hotplug_cfd() 2009-08-07 10:39:55 -07:00
softirq.c softirq: introduce tasklet_hrtimer infrastructure 2009-07-22 17:01:17 +02:00
softlockup.c
spinlock.c Allow rwlocks to re-enable interrupts 2009-04-02 19:05:11 -07:00
srcu.c
stacktrace.c
stop_machine.c cpumask: remove cpumask_t from core 2009-03-30 22:05:17 +10:30
sys.c groups: move code to kernel/groups.c 2009-06-16 19:47:48 -07:00
sys_ni.c
sysctl.c Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-28 11:05:28 -07:00
sysctl_check.c
taskstats.c
test_kprobes.c
time.c
timeconst.pl
timer.c Merge branch 'linus' into timers/core 2009-08-14 15:59:30 +02:00
tracepoint.c tracepoints: dont update zero-sized tracepoint sections 2009-03-18 19:55:00 +01:00
tsacct.c Fix fixpoint divide exception in acct_update_integrals 2009-03-09 08:13:35 -07:00
uid16.c
up.c
user.c sched: delayed cleanup of user_struct 2009-06-15 21:30:23 -07:00
user_namespace.c Fix recursive lock in free_uid()/free_user_ns() 2009-02-27 16:26:21 -08:00
utsname.c utsns: extract creeate_uts_ns() 2009-06-18 13:03:55 -07:00
utsname_sysctl.c proc_sysctl: use CONFIG_PROC_SYSCTL around ipc and utsname proc_handlers 2009-04-02 19:05:01 -07:00
wait.c locking, sched: Give waitqueue spinlocks their own lockdep classes 2009-08-10 14:43:09 +02:00
workqueue.c ftrace, workqueuetrace: make workqueue tracepoints use TRACE_EVENT macro 2009-06-02 01:10:40 +02:00