Messages in this thread | | | Date | Mon, 25 Jun 2018 17:08:41 -0700 | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 0/40] RCU ->gp_seq conversion for v4.19 |
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Hello!
This series moves from the two-variable ->gpnum and ->completed to a single-variable ->gp_seq approach. The key point is that ->gpnum and ->completed are either identical or ->gpnum is only one greater, which means that we are using a full unsigned long were a single bit would do. This series therefore applies the pre-existing grace-period sequence-number code used by expedited grace periods, _rcu_barrier(), and SRCU. This change also has the beneficial effect of allowing the grace-period state to be sampled with a single load, which will be used to improve the grace-period start code. The individual commits are as follows:
1. Introduce grace-period sequence numbers (->gp_seq) to normal RCU.
2-17. Make core RCU code use ->gp_seq instead of ->gpnum and ->completed.
18. Move from ->need_future_gp[] to ->gp_seq_needed, which allows simpler grace-period-already-requested checks.
19. Use the new ->gp_seq_needed to make rcu_nocb_wait_gp() check if a given grace has already been requested, thus reducing overhead for no-CBs CPUs.
20-26. Move RCU tracepoints to ->gp_seq.
27. Remove ->gpnum and ->completed.
28. Make simple callback acceleration refer to rdp->gp_seq_needed.
29-31. Update documentation to reflect ->gp_seq.
32. Don't funnel-lock above the leaf rcu_node structure if a grace period is in progress, thus saving an upper-level rcu_node ->lock acquisition.
33. Produce the last CleanupMore trace only if the corresponding grace-period request was quite recent, courtesy of Joel Fernandes.
34. Fix cpustart tracepoint ->gp_seq number, courtesy of Joel Fernandes.
35. Make rcu_start_this_gp() check for grace period already started.
36. Correctly handle grace-period sequence (->gp_seq) wrap in rcutorture.
37. Regularize resetting of rcu_data wrap indicator.
38-39. Rename grace-period-request variables and parameters, courtesy of Joel Fernandes.
40. Check current node rather than leaf node for requested grace period already being in progress.
Thanx, Paul
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Documentation/RCU/Design/Data-Structures/Data-Structures.html | 118 - Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html | 22 Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp-cleanup.svg | 123 - Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp-init-1.svg | 16 Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp-init-3.svg | 56 Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg | 237 +-- Documentation/RCU/Design/Memory-Ordering/TreeRCU-qs.svg | 12 Documentation/RCU/stallwarn.txt | 24 include/trace/events/rcu.h | 114 - kernel/rcu/rcu.h | 70 - kernel/rcu/rcuperf.c | 44 kernel/rcu/rcutorture.c | 93 - kernel/rcu/srcutree.c | 5 kernel/rcu/tree.c | 678 ++++------ kernel/rcu/tree.h | 40 kernel/rcu/tree_plugin.h | 54 16 files changed, 832 insertions(+), 874 deletions(-)
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