Messages in this thread | | | Date | Fri, 15 Jun 2012 14:05:50 -0700 | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 0/15] Improvements to rcu_barrier() and RT response on big systems |
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Hello!
This patch series contains improvements to the rcu_barrier() family of primitives and to latency for large systems. These are in a single series due to conflicts that would otherwise occur. The individual patches are as follows:
1. Allow the value for RCU_FANOUT_LEAF to be increased (but not decreased!) via a boot-time parameter, in turn allowing a default kernel build to be adjusted for low RCU grace-period initialization latency on a large system. 2. Work around the new default NR_CPUS=4096 by checking the boot-time-computed nr_cpu_ids, allowing this to override NR_CPUS. This again reduces RCU grace-period initialization latency for kernels built with large NR_CPUS running on small systems. 3. Shrink a macro argument to keep lines under 80 characters. 4. Add a pointer in the rcu_state structure to the corresponding member of the call_rcu() family of functions in preparation for increasing rcu_barrier() concurrency. 5. Move _rcu_barrier()'s rcu_head structures to the per-CPU per-RCU-flavor rcu_data structures so that different flavors of rcu_barrier() do not need to contend for the rcu_head structures. 6. Move rcu_barrier()'s rcu_barrier_cpu_count global variable to a new ->barrier_cpu_count field in the rcu_state structure, so that different flavors of rcu_barrier() do not need to contend for this variable. 7. Move rcu_barrier()'s rcu_barrier_completion global variable to a new ->barrier_completion field in the rcu_state structure, so that different flavors of rcu_barrier() do not need to contend for this variable. 8. Move rcu_barrier()'s rcu_barrier_mutex global variable to a new ->barrier_mutex field in the rcu_state structure, so that different flavors of rcu_barrier() do not need to contend for this variable. 9. Introduce counter scheme to allow multiple concurrent executions of a given flavor of rcu_barrier() to share work. 10. Add event tracing for _rcu_barrier(). 11. Add debugfs tracing for _rcu_barrier(). 12. Remove unnecessary per-CPU variable argument from __rcu_process_callbacks(). 13. Introduce for_each_rcu_flavor() iterator and use it. This provides a nicer way to iterate through the RCU flavors to do per-flavor processing. 14. Apply the for_each_rcu_flavor() iterator to debugfs tracing. 15. Remove dead-code gcc helper from code that is no longer ever dead.
Thanx, Paul
b/Documentation/kernel-parameters.txt | 4 b/include/trace/events/rcu.h | 45 +++++++ b/kernel/rcutree.c | 97 +++++++++++++-- b/kernel/rcutree.h | 23 ++- b/kernel/rcutree_plugin.h | 4 b/kernel/rcutree_trace.c | 2 kernel/rcutree.c | 213 +++++++++++++++++++++------------- kernel/rcutree.h | 22 ++- kernel/rcutree_plugin.h | 126 -------------------- kernel/rcutree_trace.c | 134 ++++++++++++--------- 10 files changed, 379 insertions(+), 291 deletions(-)
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