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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-08-10 14:33:17 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-10-09 14:23:36 -0700 |
| commit | 3d916a443e97169a3d88765c4e0b07ac813f439f (patch) | |
| tree | 2014eaee2f3b3a8a2fcd1311413cbf48c1e44f3c /Documentation/RCU | |
| parent | dfa0ee48ef86f79430d2be9d1e2e1b509abb3cce (diff) | |
| download | talos-obmc-linux-3d916a443e97169a3d88765c4e0b07ac813f439f.tar.gz talos-obmc-linux-3d916a443e97169a3d88765c4e0b07ac813f439f.zip | |
documentation: Slow systems can stall RCU grace periods
If a fast system has a worst-case grace-period duration of (say) ten
seconds, then running the same workload on a system ten times as slow
will get you an RCU CPU stall warning given default stall-warning
timeout settings. This commit therefore adds this possibility to
stallwarn.txt.
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/stallwarn.txt | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 21b8913acbdf..238acbd94917 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -70,6 +70,12 @@ o A periodic interrupt whose handler takes longer than the time considerably longer than normal, which can in turn result in RCU CPU stall warnings. +o Testing a workload on a fast system, tuning the stall-warning + timeout down to just barely avoid RCU CPU stall warnings, and then + running the same workload with the same stall-warning timeout on a + slow system. Note that thermal throttling and on-demand governors + can cause a single system to be sometimes fast and sometimes slow! + o A hardware or software issue shuts off the scheduler-clock interrupt on a CPU that is not in dyntick-idle mode. This problem really has happened, and seems to be most likely to |
