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Diffstat (limited to 'Documentation/RCU/trace.txt')
| -rw-r--r-- | Documentation/RCU/trace.txt | 122 |
1 files changed, 17 insertions, 105 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index c776968f446..910870b15ac 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -396,14 +396,14 @@ o Each element of the form "3/3 ..>. 0:7 ^0" represents one rcu_node The output of "cat rcu/rcu_sched/rcu_pending" looks as follows: - 0!np=26111 qsp=29 rpq=5386 cbr=1 cng=570 gpc=3674 gps=577 nn=15903 - 1!np=28913 qsp=35 rpq=6097 cbr=1 cng=448 gpc=3700 gps=554 nn=18113 - 2!np=32740 qsp=37 rpq=6202 cbr=0 cng=476 gpc=4627 gps=546 nn=20889 - 3 np=23679 qsp=22 rpq=5044 cbr=1 cng=415 gpc=3403 gps=347 nn=14469 - 4!np=30714 qsp=4 rpq=5574 cbr=0 cng=528 gpc=3931 gps=639 nn=20042 - 5 np=28910 qsp=2 rpq=5246 cbr=0 cng=428 gpc=4105 gps=709 nn=18422 - 6!np=38648 qsp=5 rpq=7076 cbr=0 cng=840 gpc=4072 gps=961 nn=25699 - 7 np=37275 qsp=2 rpq=6873 cbr=0 cng=868 gpc=3416 gps=971 nn=25147 + 0!np=26111 qsp=29 rpq=5386 cbr=1 cng=570 gpc=3674 gps=577 nn=15903 ndw=0 + 1!np=28913 qsp=35 rpq=6097 cbr=1 cng=448 gpc=3700 gps=554 nn=18113 ndw=0 + 2!np=32740 qsp=37 rpq=6202 cbr=0 cng=476 gpc=4627 gps=546 nn=20889 ndw=0 + 3 np=23679 qsp=22 rpq=5044 cbr=1 cng=415 gpc=3403 gps=347 nn=14469 ndw=0 + 4!np=30714 qsp=4 rpq=5574 cbr=0 cng=528 gpc=3931 gps=639 nn=20042 ndw=0 + 5 np=28910 qsp=2 rpq=5246 cbr=0 cng=428 gpc=4105 gps=709 nn=18422 ndw=0 + 6!np=38648 qsp=5 rpq=7076 cbr=0 cng=840 gpc=4072 gps=961 nn=25699 ndw=0 + 7 np=37275 qsp=2 rpq=6873 cbr=0 cng=868 gpc=3416 gps=971 nn=25147 ndw=0 The fields are as follows: @@ -432,6 +432,10 @@ o "gpc" is the number of times that an old grace period had o "gps" is the number of times that a new grace period had started, but this CPU was not yet aware of it. +o "ndw" is the number of times that a wakeup of an rcuo + callback-offload kthread had to be deferred in order to avoid + deadlock. + o "nn" is the number of times that this CPU needed nothing. @@ -443,7 +447,7 @@ The output of "cat rcu/rcuboost" looks as follows: balk: nt=0 egt=6541 bt=0 nb=0 ny=126 nos=0 This information is output only for rcu_preempt. Each two-line entry -corresponds to a leaf rcu_node strcuture. The fields are as follows: +corresponds to a leaf rcu_node structure. The fields are as follows: o "n:m" is the CPU-number range for the corresponding two-line entry. In the sample output above, the first entry covers @@ -530,113 +534,21 @@ 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. |