commit 5ee832dbc6770135ec8d63296af0a4374557bb79
author Eric Dumazet <dada1@cosmosbay.com> Mon Oct 17 20:01:21 2005 +0200
committer Linus Torvalds <torvalds@g5.osdl.org> Mon Oct 17 15:27:58 2005 -0700
tree 80ffdc157100df18f1c18d39f5036a9b798f2c06
parent cc675230a9ca17010694bc8bd3c69ca9adf2efef

[PATCH] rcu: keep rcu callback event counter

This makes call_rcu() keep track of how many events there are on the RCU
list, and cause a reschedule event when the list gets too long.

This helps keep RCU event lists down.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/rcupdate.h

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 4e65eb4..70191a5 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -94,6 +94,7 @@
 	long  	       	batch;           /* Batch # for current RCU batch */
 	struct rcu_head *nxtlist;
 	struct rcu_head **nxttail;
+	long            count; /* # of queued items */
 	struct rcu_head *curlist;
 	struct rcu_head **curtail;
 	struct rcu_head *donelist;

kernel/rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index dd99415..2559d4b 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -109,6 +109,10 @@
 	rdp = &__get_cpu_var(rcu_data);
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
+
+	if (unlikely(++rdp->count > 10000))
+		set_need_resched();
+
 	local_irq_restore(flags);
 }
 
@@ -140,6 +144,12 @@
 	rdp = &__get_cpu_var(rcu_bh_data);
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
+	rdp->count++;
+/*
+ *  Should we directly call rcu_do_batch() here ?
+ *  if (unlikely(rdp->count > 10000))
+ *      rcu_do_batch(rdp);
+ */
 	local_irq_restore(flags);
 }
 
@@ -157,6 +167,7 @@
 		next = rdp->donelist = list->next;
 		list->func(list);
 		list = next;
+		rdp->count--;
 		if (++count >= maxbatch)
 			break;
 	}