From 2cc78eb52bc1ae89f0a4fa5a00eb998dffde4a9f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 17 Oct 2005 09:10:15 -0700 Subject: Increase default RCU batching sharply Dipankar made RCU limit the batch size to improve latency, but that approach is unworkable: it can cause the RCU queues to grow without bounds, since the batch limiter ended up limiting the callbacks. So make the limit much higher, and start planning on instead limiting the batch size by doing RCU callbacks more often if the queue looks like it might be growing too long. Signed-off-by: Linus Torvalds --- kernel/rcupdate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/rcupdate.c') diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index bef3b6901b76..dd99415b1551 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -71,7 +71,7 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L }; /* Fake initialization required by compiler */ static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL}; -static int maxbatch = 10; +static int maxbatch = 10000; #ifndef __HAVE_ARCH_CMPXCHG /* -- cgit v1.2.2 From 5ee832dbc6770135ec8d63296af0a4374557bb79 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 17 Oct 2005 20:01:21 +0200 Subject: [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 --- kernel/rcupdate.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'kernel/rcupdate.c') diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index dd99415b1551..2559d4b8f23f 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -109,6 +109,10 @@ void fastcall call_rcu(struct rcu_head *head, 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 @@ void fastcall call_rcu_bh(struct rcu_head *head, 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 @@ static void rcu_do_batch(struct rcu_data *rdp) next = rdp->donelist = list->next; list->func(list); list = next; + rdp->count--; if (++count >= maxbatch) break; } -- cgit v1.2.2 From a241ec65aeac3d69a08a7b153cccbdb7ea35063f Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 30 Oct 2005 15:03:12 -0800 Subject: [PATCH] RCU torture-testing kernel module This patch is a rewrite of the one submitted on October 1st, using modules (http://marc.theaimsgroup.com/?l=linux-kernel&m=112819093522998&w=2). This rewrite adds a tristate CONFIG_RCU_TORTURE_TEST, which enables an intense torture test of the RCU infratructure. This is needed due to the continued changes to the RCU infrastructure to accommodate dynamic ticks, CPU hotplug, realtime, and so on. Most of the code is in a separate file that is compiled only if the CONFIG variable is set. Documentation on how to run the test and interpret the output is also included. This code has been tested on i386 and ppc64, and an earlier version of the code has received extensive testing on a number of architectures as part of the PREEMPT_RT patchset. Signed-off-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/rcupdate.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'kernel/rcupdate.c') diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 2559d4b8f23f..c4d159a21e04 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -153,6 +153,15 @@ void fastcall call_rcu_bh(struct rcu_head *head, local_irq_restore(flags); } +/* + * Return the number of RCU batches processed thus far. Useful + * for debug and statistics. + */ +long rcu_batches_completed(void) +{ + return rcu_ctrlblk.completed; +} + /* * Invoke the completed RCU callbacks. They are expected to be in * a per-cpu list. @@ -501,6 +510,7 @@ void synchronize_kernel(void) } module_param(maxbatch, int, 0); +EXPORT_SYMBOL_GPL(rcu_batches_completed); EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */ EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */ EXPORT_SYMBOL_GPL(synchronize_rcu); -- cgit v1.2.2