Hello!
This series contains SRCU updates, perhaps most notably the addition of
srcu_read_lock_fast() and srcu_read_unlock_fast(), which on my laptop are
about 20% faster than rcu_read_lock_trace() and rcu_read_unlock_trace().
There are of course drawbacks:
o Lack of CPU stall warnings.
o SRCU-fast readers permitted only where rcu_is_watching().
o A pointer-sized return value from srcu_read_lock_fast() must
be passed to the corresponding srcu_read_unlock_fast().
o In the absence of readers, a synchronize_srcu() having _fast()
readers will incur the latency of at least two normal RCU grace
periods.
o RCU Tasks Trace priority boosting could be easily added.
Boosting SRCU readers is more difficult.
Whether or not this can replace RCU Tasks Trace, it should replace the
SRCU-lite API, where the only drawback is a pointer-sized return value
from srcu_read_lock_fast() compared to the int-sized return value from
srcu_read_lock_lite(). And yes, I should have thought harder before
doing that SRCU-lite...
The series is as follows:
1. Make Tiny SRCU able to operate in preemptible kernels.
2. Define SRCU_READ_FLAVOR_ALL in terms of symbols.
3. Use ->srcu_gp_seq for rcutorture reader batch.
4. Pull ->srcu_{un,}lock_count into a new srcu_ctr structure.
5. Make SRCU readers use ->srcu_ctrs for counter selection.
6. Make Tree SRCU updates independent of ->srcu_idx.
7. Force synchronization for srcu_get_delay().
8. Rename srcu_check_read_flavor_lite() to
srcu_check_read_flavor_force().
9. Add SRCU_READ_FLAVOR_SLOWGP to flag need for synchronize_rcu().
10. Pull pointer-to-integer conversion into __srcu_ptr_to_ctr().
11. Pull integer-to-pointer conversion into __srcu_ctr_to_ptr().
12. Move SRCU Tree/Tiny definitions from srcu.h.
13. Add SRCU-fast readers.
14. Add ability to test srcu_read_{,un}lock_fast().
15. Add srcu_read_lock_fast() support using "srcu-fast".
16. Make scenario SRCU-P use srcu_read_lock_fast().
17. Fix srcu_read_unlock_{lite,nmisafe}() kernel-doc.
Thanx, Paul
------------------------------------------------------------------------
b/include/linux/srcu.h | 3
b/include/linux/srcutiny.h | 2
b/include/linux/srcutree.h | 13
b/kernel/rcu/rcu.h | 9
b/kernel/rcu/rcutorture.c | 2
b/kernel/rcu/refscale.c | 32 +
b/kernel/rcu/srcutiny.c | 6
b/kernel/rcu/srcutree.c | 2
b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-P.boot | 1
include/linux/srcu.h | 66 ++-
include/linux/srcutiny.h | 25 +
include/linux/srcutree.h | 77 +++
kernel/rcu/rcutorture.c | 9
kernel/rcu/srcutree.c | 233 +++++------
14 files changed, 332 insertions(+), 148 deletions(-)
