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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-06-17 15:53:19 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-09-28 21:38:12 -0700
commit29c00b4a1d9e277786120032aa8364631820d863 (patch)
tree23bf0c8cdb5268ef92ef9ed007639705e922b1b0 /kernel/rcutree.c
parent9d68197c05201d8edc70d58bd1d5dad05d8455e8 (diff)
downloadop-kernel-dev-29c00b4a1d9e277786120032aa8364631820d863.zip
op-kernel-dev-29c00b4a1d9e277786120032aa8364631820d863.tar.gz
rcu: Add event-tracing for RCU callback invocation
There was recently some controversy about the overhead of invoking RCU callbacks. Add TRACE_EVENT()s to obtain fine-grained timings for the start and stop of a batch of callbacks and also for each callback invoked. 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.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index a7c6bce..45dcc20 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -52,6 +52,9 @@
#include <linux/prefetch.h>
#include "rcutree.h"
+#include <trace/events/rcu.h>
+
+#include "rcu.h"
/* Data structures. */
@@ -1190,17 +1193,22 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
{
unsigned long flags;
struct rcu_head *next, *list, **tail;
- int count;
+ int bl, count;
/* If no callbacks are ready, just return.*/
- if (!cpu_has_callbacks_ready_to_invoke(rdp))
+ if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
+ trace_rcu_batch_start(0, 0);
+ trace_rcu_batch_end(0);
return;
+ }
/*
* Extract the list of ready callbacks, disabling to prevent
* races with call_rcu() from interrupt handlers.
*/
local_irq_save(flags);
+ bl = rdp->blimit;
+ trace_rcu_batch_start(rdp->qlen, bl);
list = rdp->nxtlist;
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
@@ -1218,11 +1226,12 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
debug_rcu_head_unqueue(list);
__rcu_reclaim(list);
list = next;
- if (++count >= rdp->blimit)
+ if (++count >= bl)
break;
}
local_irq_save(flags);
+ trace_rcu_batch_end(count);
/* Update count, and requeue any remaining callbacks. */
rdp->qlen -= count;
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