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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-11-30 11:21:21 -0800 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-01-23 11:44:18 -0800 |
commit | 3a19b46a5c17b12ef0691df19c676ba3da330a57 (patch) | |
tree | b9effecf9064beba8b6d55fa5a7c1fd1b56a72c4 /lib/raid6 | |
parent | 02a5c550b2738f2bfea8e1e00aa75944d71c9e18 (diff) |
rcu: Check cond_resched_rcu_qs() state less often to reduce GP overhead
Commit 4a81e8328d37 ("rcu: Reduce overhead of cond_resched() checks
for RCU") moved quiescent-state generation out of cond_resched()
and commit bde6c3aa9930 ("rcu: Provide cond_resched_rcu_qs() to force
quiescent states in long loops") introduced cond_resched_rcu_qs(), and
commit 5cd37193ce85 ("rcu: Make cond_resched_rcu_qs() apply to normal RCU
flavors") introduced the per-CPU rcu_qs_ctr variable, which is frequently
polled by the RCU core state machine.
This frequent polling can increase grace-period rate, which in turn
increases grace-period overhead, which is visible in some benchmarks
(for example, the "open1" benchmark in Anton Blanchard's "will it scale"
suite). This commit therefore reduces the rate at which rcu_qs_ctr
is polled by moving that polling into the force-quiescent-state (FQS)
machinery, and by further polling it only after the grace period has
been in effect for at least jiffies_till_sched_qs jiffies.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'lib/raid6')
0 files changed, 0 insertions, 0 deletions