Hello!
This patch series contains additional improvements to latency for
large systems (beyond those in 3.6), along with improvements to
synchronize_rcu_expedited(). It also fixes one race introduced by the
latency improvements and another that was there to start with (but made
more probable by the latency improvements). These are in a single
series due to conflicts that would otherwise occur. The individual
patches are as follows:
1-6. Move RCU grace-period initialization and cleanup into a kthread:
1. Move RCU grace-period initialization into kthread.
2. Prevent initialization-time quiescent-state race.
3. Allow RCU grace-period initialization to be preempted.
4. Move RCU grace-period cleanup into kthread.
5. Allow RCU grace-period cleanup to be preempted.
6. Break up rcu_gp_kthread() into subfunctions.
7. Prevent offline CPUs from executing RCU core code.
8. Provide an OOM handler to allow lazy callbacks to be motivated
under memory pressure.
9. Segregate rcu_state fields to improve cache locality
(Courtesy of Dimitri Sivanich).
10-13. Move RCU grace-period forcing into a kthread.
10. Move quiescent-state forcing into kthread.
11. Allow RCU quiescent-state forcing to be preempted.
12. Adjust debugfs tracing for kthread-based quiescent-state
forcing.
13. Prevent force_quiescent_state() memory contention.
14. Control grace-period duration from sysfs.
15. Make rcutree module parameters visible in sysfs.
16. Fix day-zero grace-period initialization/cleanup race.
17. Add random PROVE_RCU_DELAY to provoke initalization races.
18. Adjust for unconditional ->completed assignment.
19. Eliminate signed overflow in synchronize_rcu_expedited().
20. Reduce synchronize_rcu_expedited() latency.
21. Simplify quiescent-state detection.
22. Correctly handle reconfiguring to larger leaf fanout in the
case of CONFIG_RCU_FANOUT_EXACT=y. (New in this posting.)
23. Shrink RCU when there is a smaller number of CPUs than the
kernel was built for (NR_CPUS < nr_cpu_ids) even when the
leaf fanout did not change. (New in this posting.)
Changes from v1 (https://lkml.org/lkml/2012/8/30/171):
o Incorporated feedback from that posting (thank you Peter, Josh,
and Lai!). This involves some serious rebasing, so the patch
numbers do not match v1.
o Added patches #22 and #23 above.
Thanx, Paul
b/Documentation/RCU/trace.txt | 43 -
b/Documentation/kernel-parameters.txt | 11
b/kernel/rcutree.c | 970 ++++++++++++++++++----------------
b/kernel/rcutree.h | 28
b/kernel/rcutree_plugin.h | 131 +++-
b/kernel/rcutree_trace.c | 15
6 files changed, 680 insertions(+), 518 deletions(-)
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