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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-03-27 11:32:12 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-06-10 13:45:52 -0700
commit7807acdb6b794b3af42dfa1912edd4fba8d0b622 (patch)
tree789dfa74747a79cb3a6b148f7bd1badf148a6c6e /Documentation/RCU
parent318bdcd95938ec3a530fc789da662ce159d50d46 (diff)
rcu: Remove TINY_PREEMPT_RCU tracing documentation
Because TINY_PREEMPT_RCU is no more, this commit removes its tracing formats from the documentation. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'Documentation/RCU')
-rw-r--r--Documentation/RCU/trace.txt100
1 files changed, 4 insertions, 96 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index c776968f4463..f3778f8952da 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -530,113 +530,21 @@ o "nos" counts the number of times we balked for other
reasons, e.g., the grace period ended first.
-CONFIG_TINY_RCU and CONFIG_TINY_PREEMPT_RCU debugfs Files and Formats
+CONFIG_TINY_RCU debugfs Files and Formats
These implementations of RCU provides a single debugfs file under the
top-level directory RCU, namely rcu/rcudata, which displays fields in
-rcu_bh_ctrlblk, rcu_sched_ctrlblk and, for CONFIG_TINY_PREEMPT_RCU,
-rcu_preempt_ctrlblk.
+rcu_bh_ctrlblk and rcu_sched_ctrlblk.
The output of "cat rcu/rcudata" is as follows:
-rcu_preempt: qlen=24 gp=1097669 g197/p197/c197 tasks=...
- ttb=. btg=no ntb=184 neb=0 nnb=183 j=01f7 bt=0274
- normal balk: nt=1097669 gt=0 bt=371 b=0 ny=25073378 nos=0
- exp balk: bt=0 nos=0
rcu_sched: qlen: 0
rcu_bh: qlen: 0
-This is split into rcu_preempt, rcu_sched, and rcu_bh sections, with the
-rcu_preempt section appearing only in CONFIG_TINY_PREEMPT_RCU builds.
-The last three lines of the rcu_preempt section appear only in
-CONFIG_RCU_BOOST kernel builds. The fields are as follows:
+This is split into rcu_sched and rcu_bh sections. The field is as
+follows:
o "qlen" is the number of RCU callbacks currently waiting either
for an RCU grace period or waiting to be invoked. This is the
only field present for rcu_sched and rcu_bh, due to the
short-circuiting of grace period in those two cases.
-
-o "gp" is the number of grace periods that have completed.
-
-o "g197/p197/c197" displays the grace-period state, with the
- "g" number being the number of grace periods that have started
- (mod 256), the "p" number being the number of grace periods
- that the CPU has responded to (also mod 256), and the "c"
- number being the number of grace periods that have completed
- (once again mode 256).
-
- Why have both "gp" and "g"? Because the data flowing into
- "gp" is only present in a CONFIG_RCU_TRACE kernel.
-
-o "tasks" is a set of bits. The first bit is "T" if there are
- currently tasks that have recently blocked within an RCU
- read-side critical section, the second bit is "N" if any of the
- aforementioned tasks are blocking the current RCU grace period,
- and the third bit is "E" if any of the aforementioned tasks are
- blocking the current expedited grace period. Each bit is "."
- if the corresponding condition does not hold.
-
-o "ttb" is a single bit. It is "B" if any of the blocked tasks
- need to be priority boosted and "." otherwise.
-
-o "btg" indicates whether boosting has been carried out during
- the current grace period, with "exp" indicating that boosting
- is in progress for an expedited grace period, "no" indicating
- that boosting has not yet started for a normal grace period,
- "begun" indicating that boosting has bebug for a normal grace
- period, and "done" indicating that boosting has completed for
- a normal grace period.
-
-o "ntb" is the total number of tasks subjected to RCU priority boosting
- periods since boot.
-
-o "neb" is the number of expedited grace periods that have had
- to resort to RCU priority boosting since boot.
-
-o "nnb" is the number of normal grace periods that have had
- to resort to RCU priority boosting since boot.
-
-o "j" is the low-order 16 bits of the jiffies counter in hexadecimal.
-
-o "bt" is the low-order 16 bits of the value that the jiffies counter
- will have at the next time that boosting is scheduled to begin.
-
-o In the line beginning with "normal balk", the fields are as follows:
-
- o "nt" is the number of times that the system balked from
- boosting because there were no blocked tasks to boost.
- Note that the system will balk from boosting even if the
- grace period is overdue when the currently running task
- is looping within an RCU read-side critical section.
- There is no point in boosting in this case, because
- boosting a running task won't make it run any faster.
-
- o "gt" is the number of times that the system balked
- from boosting because, although there were blocked tasks,
- none of them were preventing the current grace period
- from completing.
-
- o "bt" is the number of times that the system balked
- from boosting because boosting was already in progress.
-
- o "b" is the number of times that the system balked from
- boosting because boosting had already completed for
- the grace period in question.
-
- o "ny" is the number of times that the system balked from
- boosting because it was not yet time to start boosting
- the grace period in question.
-
- o "nos" is the number of times that the system balked from
- boosting for inexplicable ("not otherwise specified")
- reasons. This can actually happen due to races involving
- increments of the jiffies counter.
-
-o In the line beginning with "exp balk", the fields are as follows:
-
- o "bt" is the number of times that the system balked from
- boosting because there were no blocked tasks to boost.
-
- o "nos" is the number of times that the system balked from
- boosting for inexplicable ("not otherwise specified")
- reasons.

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