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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-11-29 18:57:13 -0500
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 13:32:09 -0500
commitdff1672d9199fffddb58fa7970ccf59005fc35f3 (patch)
treea9740f65dfc203d183cb06ce0faeed0de5cef58b /kernel/rcutree.c
parentfacc4e159672b4ed10aa18147bfa187b013c9505 (diff)
rcu: Keep invoking callbacks if CPU otherwise idle
The rcu_do_batch() function that invokes callbacks for TREE_RCU and TREE_PREEMPT_RCU normally throttles callback invocation to avoid degrading scheduling latency. However, as long as the CPU would otherwise be idle, there is no downside to continuing to invoke any callbacks that have passed through their grace periods. In fact, processing such callbacks in a timely manner has the benefit of increasing the probability that the CPU can enter the power-saving dyntick-idle mode. Therefore, this commit allows callback invocation to continue beyond the preset limit as long as the scheduler does not have some other task to run and as long as context is that of the idle task or the relevant RCU kthread. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c0ed3765ec39..4ec4b14cfba6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1403,7 +1403,10 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
1403 debug_rcu_head_unqueue(list); 1403 debug_rcu_head_unqueue(list);
1404 __rcu_reclaim(rsp->name, list); 1404 __rcu_reclaim(rsp->name, list);
1405 list = next; 1405 list = next;
1406 if (++count >= bl) 1406 /* Stop only if limit reached and CPU has something to do. */
1407 if (++count >= bl &&
1408 (need_resched() ||
1409 (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
1407 break; 1410 break;
1408 } 1411 }
1409 1412