diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-04-14 17:39:26 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-05-10 11:08:35 -0700 |
| commit | d21670acab9fcb4bc74a40b68a6941059234c55c (patch) | |
| tree | 6a4c054bc4dbadf0524b4e221889a8da558dbdaf /kernel/rcutree.h | |
| parent | 4a90a0681cf6cd21cd444184302aa045156486b3 (diff) | |
rcu: reduce the number of spurious RCU_SOFTIRQ invocations
Lai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and
traced this down to the fact that the current grace-period machinery
will uselessly raise RCU_SOFTIRQ when a given CPU needs to go through
a quiescent state, but has not yet done so. In this situation, there
might well be nothing that RCU_SOFTIRQ can do, and the overhead can be
worth worrying about in the ksoftirqd case. This patch therefore avoids
raising RCU_SOFTIRQ in this situation.
Changes since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan):
o Omit the rcu_qs_pending() prechecks, as they aren't that
much less expensive than the quiescent-state checks.
o Merge with the set_need_resched() patch that reduces IPIs.
o Add the new n_rp_report_qs field to the rcu_pending tracing output.
o Update the tracing documentation accordingly.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.h')
| -rw-r--r-- | kernel/rcutree.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 11f171121ad..14c040b18ed 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -223,6 +223,7 @@ struct rcu_data { /* 5) __rcu_pending() statistics. */ unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ unsigned long n_rp_qs_pending; + unsigned long n_rp_report_qs; unsigned long n_rp_cb_ready; unsigned long n_rp_cpu_needs_gp; unsigned long n_rp_gp_completed; |