Messages in this thread | | | Date | Wed, 26 Apr 2017 20:42:42 -0700 | From | "Paul E. McKenney" <> | Subject | [GIT PULL rcu/urgent] Auto-expedite initial SRCU grace periods |
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Hello, Ingo,
This series greatly reduces the performance degradation of Tree SRCU on a CPU-hotplug stress test. The effect was not subtle: Mike Galbraith measured Classic SRCU at 55 seconds and Tree SRCU at more than 16 -minutes- for this test. Mike collected ftrace data that showed that Classic SRCU was auto-expediting invocations of synchronize_srcu() that found SRCU completely idle. This series therefore adds this auto-expedite capability to Tree SRCU, bringing the performance shortfall to less than ten seconds, which is a great improvement over the initial shortfall of 15 minutes.
I will continue tuning, but this improvement seemed worth a pull request, in order to get the base solution some more test time in -tip. Note that two of the commits are not strictly necessary, but they are reasonably simple, they conflict with the three main commits, and the risk of disentangling them seemed to greatly exceed the risk of pushing them in. Of course, if you believe that they really should be delayed, please let me know and I can disentangle them. They are: (1) c7e88067c1ae ("srcu: Exact tracking of srcu_data structures containing callbacks") and (2) 7f6733c3c648 ("srcu: Make rcutorture writer stalls print SRCU GP state").
These commits are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/urgent
for you to fetch changes up to 22607d66bbc3e81140d3bcf08894f4378eb36428:
srcu: Specify auto-expedite holdoff time (2017-04-26 16:32:17 -0700)
---------------------------------------------------------------- Paul E. McKenney (5): srcu: Exact tracking of srcu_data structures containing callbacks srcu: Make rcutorture writer stalls print SRCU GP state srcu: Expedited grace periods with reduced memory contention srcu: Expedite first synchronize_srcu() when idle srcu: Specify auto-expedite holdoff time
Documentation/admin-guide/kernel-parameters.txt | 8 + include/linux/srcuclassic.h | 14 ++ include/linux/srcutiny.h | 12 ++ include/linux/srcutree.h | 13 +- kernel/rcu/rcutorture.c | 8 +- kernel/rcu/srcutree.c | 242 ++++++++++++++++++++---- kernel/rcu/tree.c | 12 +- 7 files changed, 255 insertions(+), 54 deletions(-)
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