linux.git/Documentation/RCU, branch v2.6.38

rcu: update documentation/comments for Lai's adoption patch

2010-11-30T06:01:59+00:00

Lai's RCU-callback immediate-adoption patch changes the RCU tracing
output, so update tracing.txt.  Also update a few comments to clarify
the synchronization design.

Signed-off-by: Paul E. McKenney

rcu: document TINY_RCU and TINY_PREEMPT_RCU tracing.

2010-11-30T06:01:56+00:00

Add the required verbiage to Documentation/RCU/trace.txt.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Paul E. McKenney

rcu: Add tracing data to support queueing models

2010-09-23T16:16:53+00:00

The current tracing data is not sufficient to deduce the average time
that a callback spends waiting for a grace period to end.  Add three
per-CPU counters recording the number of callbacks invoked (ci), the
number of callbacks orphaned (co), and the number of callbacks adopted
(ca).  Given the existing callback queue length (ql), the average wait
time in absence of CPU hotplug operations is ql/ci.  The units of wait
time will be in terms of the duration over which ci was measured.

In the presence of CPU hotplug operations, there is room for argument,
but ql/(ci-co+ca) won't steer you too far wrong.

Also fixes a typo called out by Lucas De Marchi .

Signed-off-by: Paul E. McKenney

rcu: upgrade stallwarn.txt documentation for CPU-bound RT processes

2010-08-23T23:34:02+00:00

CPU-bound real-time processes can cause RCU CPU stall warnings, and
much other trouble as well.  Document the fact that they can cause
RCU CPU stall warnings.

Suggested-by: Darren Hart 
Signed-off-by: Paul E. McKenney

rcu: document ways of stalling updates in low-memory situations

2010-08-20T16:00:14+00:00

Signed-off-by: Paul E. McKenney

rcu: add shiny new debug assists to Documentation/RCU/checklist.txt

2010-08-20T00:18:01+00:00

Add a section describing PROVE_RCU, DEBUG_OBJECTS_RCU_HEAD, and
the __rcu sparse checking to the RCU checklist.

Suggested-by: David Miller 
Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

Documentation: update broken web addresses.

2010-08-04T13:21:40+00:00

Below you will find an updated version from the original series bunching all patches into one big patch
updating broken web addresses that are located in Documentation/*
Some of the addresses date as far far back as 1995 etc... so searching became a bit difficult,
the best way to deal with these is to use web.archive.org to locate these addresses that are outdated.
Now there are also some addresses pointing to .spec files some are located, but some(after searching
on the companies site)where still no where to be found. In this case I just changed the address
to the company site this way the users can contact the company and they can locate them for the users.

Signed-off-by: Justin P. Mattock 
Signed-off-by: Thomas Weber 
Signed-off-by: Mike Frysinger 
Cc: Paulo Marques 
Cc: Randy Dunlap 
Cc: Michael Neuling 
Signed-off-by: Jiri Kosina

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2010-05-18T15:27:54+00:00

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (49 commits)
  stop_machine: Move local variable closer to the usage site in cpu_stop_cpu_callback()
  sched, wait: Use wrapper functions
  sched: Remove a stale comment
  ondemand: Make the iowait-is-busy time a sysfs tunable
  ondemand: Solve a big performance issue by counting IOWAIT time as busy
  sched: Intoduce get_cpu_iowait_time_us()
  sched: Eliminate the ts->idle_lastupdate field
  sched: Fold updating of the last_update_time_info into update_ts_time_stats()
  sched: Update the idle statistics in get_cpu_idle_time_us()
  sched: Introduce a function to update the idle statistics
  sched: Add a comment to get_cpu_idle_time_us()
  cpu_stop: add dummy implementation for UP
  sched: Remove rq argument to the tracepoints
  rcu: need barrier() in UP synchronize_sched_expedited()
  sched: correctly place paranioa memory barriers in synchronize_sched_expedited()
  sched: kill paranoia check in synchronize_sched_expedited()
  sched: replace migration_thread with cpu_stop
  stop_machine: reimplement using cpu_stop
  cpu_stop: implement stop_cpu[s]()
  sched: Fix select_idle_sibling() logic in select_task_rq_fair()
  ...

rcu: improve the RCU CPU-stall warning documentation

2010-05-10T18:08:35+00:00

The existing Documentation/RCU/stallwarn.txt has proven unhelpful, so
rework it a bit.  In particular, show how to interpret the stall-warning
messages.

Signed-off-by: Paul E. McKenney

rcu: reduce the number of spurious RCU_SOFTIRQ invocations

2010-05-10T18:08:35+00:00

Lai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and
traced this down to the fact that the current grace-period machinery
will uselessly raise RCU_SOFTIRQ when a given CPU needs to go through
a quiescent state, but has not yet done so.  In this situation, there
might well be nothing that RCU_SOFTIRQ can do, and the overhead can be
worth worrying about in the ksoftirqd case.  This patch therefore avoids
raising RCU_SOFTIRQ in this situation.

Changes since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan):

o	Omit the rcu_qs_pending() prechecks, as they aren't that
	much less expensive than the quiescent-state checks.

o	Merge with the set_need_resched() patch that reduces IPIs.

o	Add the new n_rp_report_qs field to the rcu_pending tracing output.

o	Update the tracing documentation accordingly.

Signed-off-by: Lai Jiangshan 
Signed-off-by: Paul E. McKenney