john stultz a092ff0f90 time: Implement logarithmic time accumulation ... Accumulating one tick at a time works well unless we're using NOHZ. Then it can be an issue, since we may have to run through the loop a few thousand times, which can increase timer interrupt caused latency. The current solution was to accumulate in half-second intervals with NOHZ. This kept the number of loops down, however it did slightly change how we make NTP adjustments. While not an issue with NTPd users, as NTPd makes adjustments over a longer period of time, other adjtimex() users have noticed the half-second granularity with which we can apply frequency changes to the clock. For instance, if a application tries to apply a 100ppm frequency correction for 20ms to correct a 2us offset, with NOHZ they either get no correction, or a 50us correction. Now, there will always be some granularity error for applying frequency corrections. However with users sensitive to this error have seen a 50-500x increase with NOHZ compared to running without NOHZ. So I figured I'd try another approach then just simply increasing the interval. My approach is to consume the time interval logarithmically. This reduces the number of times through the loop needed keeping latency down, while still preserving the original granularity error for adjtimex() changes. Further, this change allows us to remove the xtime_cache code (patch to follow), as xtime is always within one tick of the current time, instead of the half-second updates it saw before. An earlier version of this patch has been shipping to x86 users in the RedHat MRG releases for awhile without issue, but I've reworked this version to be even more careful about avoiding possible overflows if the shift value gets too large. Signed-off-by: John Stultz <johnstul@us.ibm.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: John Kacur <jkacur@redhat.com> Cc: Clark Williams <williams@redhat.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> LKML-Reference: <1254525473.7741.88.camel@localhost.localdomain> Signed-off-by: Ingo Molnar <mingo@elte.hu>		2009-10-05 13:51:48 +02:00
..
gcov	microblaze: Enable GCOV_PROFILE_ALL	2009-09-21 14:29:21 +02:00
irq	Merge branch 'irq-threaded-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-11 13:21:31 -07:00
power	headers: utsname.h redux	2009-09-23 18:13:10 -07:00
time	time: Implement logarithmic time accumulation	2009-10-05 13:51:48 +02:00
trace	Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-26 10:13:54 -07:00
.gitignore
acct.c	bsdacct: switch credentials for writing to the accounting file	2009-08-24 11:33:40 +10:00
async.c	async: Fix lack of boot-time console due to insufficient synchronization	2009-06-08 12:31:53 -07:00
audit_tree.c	Fix rule eviction order for AUDIT_DIR	2009-06-24 00:02:38 -04:00
audit_watch.c	Audit: reorganize struct audit_watch to save 8 bytes	2009-09-24 03:50:25 -04:00
audit.c	Audit: send signal info if selinux is disabled	2009-09-24 03:50:26 -04:00
audit.h	Fix rule eviction order for AUDIT_DIR	2009-06-24 00:02:38 -04:00
auditfilter.c	Audit: clean up all op= output to include string quoting	2009-06-24 00:00:52 -04:00
auditsc.c	Audit: rearrange audit_context to save 16 bytes per struct	2009-09-24 03:50:26 -04:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c	cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time	2009-09-24 07:20:58 -07:00
cgroup.c	cgroup: catch bad css refcnt at css_put	2009-10-01 16:11:12 -07:00
compat.c	signals: implement sys_rt_tgsigqueueinfo	2009-04-30 19:24:24 +02:00
configs.c
cpu.c	Merge branch 'x86-pat-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-15 09:19:38 -07:00
cpuset.c	cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time	2009-09-24 07:20:58 -07:00
cred-internals.h
cred.c	creds_are_invalid() needs to be exported for use by modules:	2009-09-23 11:02:26 -07:00
delayacct.c	headers: taskstats_kern.h trim	2009-09-18 09:48:52 -07:00
dma.c
exec_domain.c	Get rid of indirect include of fs_struct.h	2009-03-31 23:00:27 -04:00
exit.c	task_struct cleanup: move binfmt field to mm_struct	2009-09-24 07:21:05 -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	task_struct cleanup: move binfmt field to mm_struct	2009-09-24 07:21:05 -07:00
freezer.c	sched: fix nr_uninterruptible accounting of frozen tasks really	2009-07-18 14:19:53 +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
futex.c	futex: Add memory barrier commentary to futex_wait_queue_me()	2009-09-24 22:30:10 +02:00
groups.c	groups: move code to kernel/groups.c	2009-06-16 19:47:48 -07:00
hrtimer.c	Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-27 10:39:04 -07:00
hung_task.c	sysctl: remove "struct file *" argument of ->proc_handler	2009-09-24 07:21:04 -07:00
itimer.c	itimers: Add tracepoints for itimer	2009-08-29 14:10:07 +02:00
kallsyms.c	kallsyms: use new arch_is_kernel_text()	2009-09-23 07:39:30 -07:00
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	kfifo: Use "const" definitions	2009-09-19 13:13:17 -07:00
kgdb.c	sysrq, intel_fb: fix sysrq g collision	2009-05-15 07:56:24 -05:00
kmod.c	Revert "kmod: fix race in usermodehelper code"	2009-09-23 18:12:10 -07:00
kprobes.c	const: constify remaining file_operations	2009-10-01 16:11:11 -07:00
ksysfs.c
kthread.c	sched: Keep kthreads at default priority	2009-09-09 17:30:06 +02:00
latencytop.c
lockdep_internals.h	lockdep: BFS cleanup	2009-07-24 10:53:29 +02:00
lockdep_proc.c	seq_file: constify seq_operations	2009-09-23 07:39:29 -07:00
lockdep_states.h
lockdep.c	lockdep: use new arch_is_kernel_data()	2009-09-23 07:39:30 -07:00
Makefile	cgroups: move the cgroup debug subsys into cgroup.c to access internal state	2009-09-24 07:20:57 -07:00
module.c	module: fix up CONFIG_KALLSYMS=n build.	2009-10-01 16:11:11 -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: let ss->can_attach and ss->attach do whole threadgroups at a time	2009-09-24 07:20:58 -07:00
nsproxy.c	nsproxy: extract create_nsproxy()	2009-06-18 13:03:56 -07:00
panic.c	trivial: Correct print_tainted routine name in comment	2009-09-21 15:14:53 +02:00
params.c	param: allow whitespace as kernel parameter separator	2009-09-25 00:32:58 +09:30
perf_event.c	const: mark struct vm_struct_operations	2009-09-27 11:39:25 -07:00
pid_namespace.c	pidns: deny CLONE_PARENT|CLONE_NEWPID combination	2009-09-24 07:21:04 -07:00
pid.c	mm: also use alloc_large_system_hash() for the PID hash table	2009-09-22 07:17:38 -07:00
pm_qos_params.c
posix-cpu-timers.c	itimers: Add tracepoints for itimer	2009-08-29 14:10:07 +02:00
posix-timers.c	time: Introduce CLOCK_REALTIME_COARSE	2009-08-21 21:43:46 +02:00
printk.c	printk: add printk_delay to make messages readable for some scenarios	2009-09-23 07:39:28 -07:00
profile.c	kernel/profile.c: Switch /proc/irq/prof_cpu_mask to seq_file	2009-09-20 20:15:40 +02:00
ptrace.c	ptrace: __ptrace_detach: do __wake_up_parent() if we reap the tracee	2009-09-24 07:20:59 -07:00
rcupdate.c	rcu: Fix whitespace inconsistencies	2009-09-19 08:53:22 +02:00
rcutorture.c	rcu: Fix whitespace inconsistencies	2009-09-19 08:53:22 +02:00
rcutree_plugin.h	rcu: Fix whitespace inconsistencies	2009-09-19 08:53:22 +02:00
rcutree_trace.c	const: constify remaining file_operations	2009-10-01 16:11:11 -07:00
rcutree.c	rcu: Fix whitespace inconsistencies	2009-09-19 08:53:22 +02:00
rcutree.h	rcu: Fix whitespace inconsistencies	2009-09-19 08:53:22 +02:00
relay.c	const: mark struct vm_struct_operations	2009-09-27 11:39:25 -07:00
res_counter.c	memcg: some modification to softlimit under hierarchical memory reclaim.	2009-10-01 16:11:13 -07:00
resource.c	walk system ram range	2009-09-23 07:39:41 -07:00
rtmutex_common.h	rt_mutex: add proxy lock routines	2009-04-06 11:14:02 +02:00
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
rwsem.c
sched_clock.c	sched_clock: Fix atomicity/continuity bug by using cmpxchg64()	2009-09-30 22:56:10 +02:00
sched_cpupri.c	sched: Add new prio to cpupri before removing old prio	2009-08-02 14:26:09 +02:00
sched_cpupri.h
sched_debug.c	sched: Add new wakeup preemption mode: WAKEUP_RUNNING	2009-09-17 10:17:25 +02:00
sched_fair.c	sysctl: remove "struct file *" argument of ->proc_handler	2009-09-24 07:21:04 -07:00
sched_features.h	sched: Add new wakeup preemption mode: WAKEUP_RUNNING	2009-09-17 10:17:25 +02:00
sched_idletask.c	sched: Simplify sys_sched_rr_get_interval() system call	2009-09-21 09:53:55 +02:00
sched_rt.c	sched: Simplify sys_sched_rr_get_interval() system call	2009-09-21 09:53:55 +02:00
sched_stats.h
sched.c	const: constify remaining file_operations	2009-10-01 16:11:11 -07:00
seccomp.c
semaphore.c
signal.c	signals: inline __fatal_signal_pending	2009-09-24 07:21:01 -07:00
slow-work.c	sysctl: remove "struct file *" argument of ->proc_handler	2009-09-24 07:21:04 -07:00
smp.c	cpumask: remove arch_send_call_function_ipi	2009-09-24 09:34:47 +09:30
softirq.c	softirq: add BLOCK_IOPOLL to softirq_to_name	2009-09-17 15:53:44 -04:00
softlockup.c	sysctl: remove "struct file *" argument of ->proc_handler	2009-09-24 07:21:04 -07:00
spinlock.c	locking: Allow arch-inlined spinlocks	2009-08-31 18:08:50 +02:00
srcu.c
stacktrace.c
stop_machine.c
sys_ni.c	Merge branch 'master' of /home/davem/src/GIT/linux-2.6/	2009-09-24 15:13:11 -07:00
sys.c	Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6	2009-09-24 07:53:22 -07:00
sysctl_check.c
sysctl.c	Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6	2009-09-24 07:53:22 -07:00
taskstats.c	genetlink: make netns aware	2009-07-12 14:03:27 -07:00
test_kprobes.c
time.c	time: Prevent 32 bit overflow with set_normalized_timespec()	2009-09-15 10:17:30 +02:00
timeconst.pl
timer.c	Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-23 09:46:15 -07:00
tracepoint.c	trivial: fix typo "to to" in multiple files	2009-09-21 15:14:55 +02:00
tsacct.c
uid16.c	headers: utsname.h redux	2009-09-23 18:13:10 -07:00
up.c
user_namespace.c
user.c	sched: delayed cleanup of user_struct	2009-06-15 21:30:23 -07:00
utsname_sysctl.c	sysctl: remove "struct file *" argument of ->proc_handler	2009-09-24 07:21:04 -07:00
utsname.c	utsns: extract creeate_uts_ns()	2009-06-18 13:03:55 -07:00
wait.c	locking, sched: Give waitqueue spinlocks their own lockdep classes	2009-08-10 14:43:09 +02:00
workqueue.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2009-09-11 13:23:18 -07:00