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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-08-19 21:35:53 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-11-16 10:05:56 -0800
commit3fbfbf7a3b66ec424042d909f14ba2ddf4372ea8 (patch)
treecc364c320a6e23927ecc154a8ef8021dc7d1a9e8 /kernel/rcutree_trace.c
parentaac1cda34b84a9411d6b8d18c3658f094c834911 (diff)
downloadlinaro-lsk-3fbfbf7a3b66ec424042d909f14ba2ddf4372ea8.tar.gz
rcu: Add callback-free CPUs
RCU callback execution can add significant OS jitter and also can degrade both scheduling latency and, in asymmetric multiprocessors, energy efficiency. This commit therefore adds the ability for selected CPUs ("rcu_nocbs=" boot parameter) to have their callbacks offloaded to kthreads. If the "rcu_nocb_poll" boot parameter is also specified, these kthreads will do polling, removing the need for the offloaded CPUs to do wakeups. At least one CPU must be doing normal callback processing: currently CPU 0 cannot be selected as a no-CBs CPU. In addition, attempts to offline the last normal-CBs CPU will fail. This feature was inspired by Jim Houston's and Joe Korty's JRCU, and this commit includes fixes to problems located by Fengguang Wu's kbuild test robot. [ paulmck: Added gfp.h include file as suggested by Fengguang Wu. ] 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_trace.c')
-rw-r--r--kernel/rcutree_trace.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index f9512687a6e..3189f9aa3e8 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -113,6 +113,8 @@ static char convert_kthread_status(unsigned int kthread_status)
static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
{
+ long ql, qll;
+
if (!rdp->beenonline)
return;
seq_printf(m, "%3d%cc=%ld g=%ld pq=%d qp=%d",
@@ -126,8 +128,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
rdp->dynticks->dynticks_nmi_nesting,
rdp->dynticks_fqs);
seq_printf(m, " of=%lu", rdp->offline_fqs);
+ rcu_nocb_q_lengths(rdp, &ql, &qll);
+ qll += rdp->qlen_lazy;
+ ql += rdp->qlen;
seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
- rdp->qlen_lazy, rdp->qlen,
+ qll, ql,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_TAIL] !=