From b1f77b0581b8fd837acb4a973f7d5496cae6efee Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 13 Mar 2009 03:20:49 +0100 Subject: kmemtrace, rcu: fix linux/rcutree.h and linux/rcuclassic.h dependencies Impact: build fix for all non-x86 architectures We want to remove percpu.h from rcuclassic.h/rcutree.h (for upcoming kmemtrace changes) but that would break the DECLARE_PER_CPU based declarations in these files. Move the quiescent counter management functions to their respective RCU implementation .c files - they were slightly above the inlining limit anyway. Cc: Pekka Enberg Cc: Eduard - Gabriel Munteanu Cc: paulmck@linux.vnet.ibm.com LKML-Reference: <1237898630.25315.83.camel@penberg-laptop> Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) (limited to 'kernel/rcutree.c') diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 97ce31579ec..a2015edfe16 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -72,11 +72,31 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); .n_force_qs_ngp = 0, \ } -struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state); -DEFINE_PER_CPU(struct rcu_data, rcu_data); +static struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state); +static DEFINE_PER_CPU(struct rcu_data, rcu_data); -struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); -DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); +static struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); +static DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); + +/* + * Increment the quiescent state counter. + * The counter is a bit degenerated: We do not need to know + * how many quiescent states passed, just if there was at least + * one since the start of the grace period. Thus just a flag. + */ +void rcu_qsctr_inc(int cpu) +{ + struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + rdp->passed_quiesc = 1; + rdp->passed_quiesc_completed = rdp->completed; +} + +void rcu_bh_qsctr_inc(int cpu) +{ + struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); + rdp->passed_quiesc = 1; + rdp->passed_quiesc_completed = rdp->completed; +} #ifdef CONFIG_NO_HZ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { -- cgit v1.2.3-70-g09d2 From 6258c4fb59e77d748f7efc2c137ad420372edd07 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 25 Mar 2009 16:42:24 +0100 Subject: kmemtrace, rcu: fix rcu_tree_trace.c data structure dependencies Impact: cleanup We want to remove rcutree internals from the public rcutree.h file for upcoming kmemtrace changes - but kernel/rcutree_trace.c depends on them. Introduce kernel/rcutree.h for internal definitions. (Probably all the other data types from include/linux/rcutree.h could be moved here too - except rcu_data.) Cc: Pekka Enberg Cc: Eduard - Gabriel Munteanu Cc: paulmck@linux.vnet.ibm.com LKML-Reference: <1237898630.25315.83.camel@penberg-laptop> Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 8 ++++---- kernel/rcutree.h | 10 ++++++++++ kernel/rcutree_trace.c | 2 ++ 3 files changed, 16 insertions(+), 4 deletions(-) create mode 100644 kernel/rcutree.h (limited to 'kernel/rcutree.c') diff --git a/kernel/rcutree.c b/kernel/rcutree.c index a2015edfe16..7f326692257 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -72,11 +72,11 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); .n_force_qs_ngp = 0, \ } -static struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state); -static DEFINE_PER_CPU(struct rcu_data, rcu_data); +struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state); +DEFINE_PER_CPU(struct rcu_data, rcu_data); -static struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); -static DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); +struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); +DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); /* * Increment the quiescent state counter. diff --git a/kernel/rcutree.h b/kernel/rcutree.h new file mode 100644 index 00000000000..5e872bbf07f --- /dev/null +++ b/kernel/rcutree.h @@ -0,0 +1,10 @@ + +/* + * RCU implementation internal declarations: + */ +extern struct rcu_state rcu_state; +DECLARE_PER_CPU(struct rcu_data, rcu_data); + +extern struct rcu_state rcu_bh_state; +DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); + diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index d6db3e83782..4ee954f6a8d 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -43,6 +43,8 @@ #include #include +#include "rcutree.h" + static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) -- cgit v1.2.3-70-g09d2 From ef631b0ca01655d24e9ca7e199262c4a46416a26 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 13 Apr 2009 21:31:16 -0700 Subject: rcu: Make hierarchical RCU less IPI-happy This patch fixes a hierarchical-RCU performance bug located by Anton Blanchard. The problem stems from a misguided attempt to provide a work-around for jiffies-counter failure. This work-around uses a per-CPU n_rcu_pending counter, which is incremented on each call to rcu_pending(), which in turn is called from each scheduling-clock interrupt. Each CPU then treats this counter as a surrogate for the jiffies counter, so that if the jiffies counter fails to advance, the per-CPU n_rcu_pending counter will cause RCU to invoke force_quiescent_state(), which in turn will (among other things) send resched IPIs to CPUs that have thus far failed to pass through an RCU quiescent state. Unfortunately, each CPU resets only its own counter after sending a batch of IPIs. This means that the other CPUs will also (needlessly) send -another- round of IPIs, for a full N-squared set of IPIs in the worst case every three scheduler-clock ticks until the grace period finally ends. It is not reasonable for a given CPU to reset each and every n_rcu_pending for all the other CPUs, so this patch instead simply disables the jiffies-counter "training wheels", thus eliminating the excessive IPIs. Note that the jiffies-counter IPIs do not have this problem due to the fact that the jiffies counter is global, so that the CPU sending the IPIs can easily reset things, thus preventing the other CPUs from sending redundant IPIs. Note also that the n_rcu_pending counter remains, as it will continue to be used for tracing. It may also see use to update the jiffies counter, should an appropriate kick-the-jiffies-counter API appear. Located-by: Anton Blanchard Tested-by: Anton Blanchard Signed-off-by: Paul E. McKenney Cc: anton@samba.org Cc: akpm@linux-foundation.org Cc: dipankar@in.ibm.com Cc: manfred@colorfullife.com Cc: cl@linux-foundation.org Cc: josht@linux.vnet.ibm.com Cc: schamp@sgi.com Cc: niv@us.ibm.com Cc: dvhltc@us.ibm.com Cc: ego@in.ibm.com Cc: laijs@cn.fujitsu.com Cc: rostedt@goodmis.org Cc: peterz@infradead.org Cc: penberg@cs.helsinki.fi Cc: andi@firstfloor.org Cc: "Paul E. McKenney" LKML-Reference: <12396834793575-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/rcutree.h | 3 +-- kernel/rcutree.c | 19 ++++--------------- kernel/rcutree_trace.c | 14 +++++--------- 3 files changed, 10 insertions(+), 26 deletions(-) (limited to 'kernel/rcutree.c') diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 0cdda00f2b2..58b2aa5312b 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -161,9 +161,8 @@ struct rcu_data { unsigned long offline_fqs; /* Kicked due to being offline. */ unsigned long resched_ipi; /* Sent a resched IPI. */ - /* 5) state to allow this CPU to force_quiescent_state on others */ + /* 5) For future __rcu_pending statistics. */ long n_rcu_pending; /* rcu_pending() calls since boot. */ - long n_rcu_pending_force_qs; /* when to force quiescent states. */ int cpu; }; diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 7f326692257..d2a372fb0b9 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -530,8 +530,6 @@ static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) rdp->qs_pending = 1; rdp->passed_quiesc = 0; rdp->gpnum = rsp->gpnum; - rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending + - RCU_JIFFIES_TILL_FORCE_QS; } /* @@ -578,8 +576,6 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) rsp->gpnum++; rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending + - RCU_JIFFIES_TILL_FORCE_QS; record_gp_stall_check_time(rsp); dyntick_record_completed(rsp, rsp->completed - 1); note_new_gpnum(rsp, rdp); @@ -1055,7 +1051,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) { unsigned long flags; long lastcomp; - struct rcu_data *rdp = rsp->rda[smp_processor_id()]; struct rcu_node *rnp = rcu_get_root(rsp); u8 signaled; @@ -1066,16 +1061,13 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) return; /* Someone else is already on the job. */ } if (relaxed && - (long)(rsp->jiffies_force_qs - jiffies) >= 0 && - (rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) >= 0) + (long)(rsp->jiffies_force_qs - jiffies) >= 0) goto unlock_ret; /* no emergency and done recently. */ rsp->n_force_qs++; spin_lock(&rnp->lock); lastcomp = rsp->completed; signaled = rsp->signaled; rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending + - RCU_JIFFIES_TILL_FORCE_QS; if (lastcomp == rsp->gpnum) { rsp->n_force_qs_ngp++; spin_unlock(&rnp->lock); @@ -1144,8 +1136,7 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) * If an RCU GP has gone long enough, go check for dyntick * idle CPUs and, if needed, send resched IPIs. */ - if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 || - (rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0) + if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) force_quiescent_state(rsp, 1); /* @@ -1230,8 +1221,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), if (unlikely(++rdp->qlen > qhimark)) { rdp->blimit = LONG_MAX; force_quiescent_state(rsp, 0); - } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 || - (rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0) + } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) force_quiescent_state(rsp, 1); local_irq_restore(flags); } @@ -1290,8 +1280,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) /* Has an RCU GP gone long enough to send resched IPIs &c? */ if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) && - ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 || - (rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0)) + ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) return 1; /* nothing to do */ diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index 4ee954f6a8d..4b1875ba940 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -49,14 +49,12 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) return; - seq_printf(m, "%3d%cc=%ld g=%ld pq=%d pqc=%ld qp=%d rpfq=%ld rp=%x", + seq_printf(m, "%3d%cc=%ld g=%ld pq=%d pqc=%ld qp=%d", rdp->cpu, cpu_is_offline(rdp->cpu) ? '!' : ' ', rdp->completed, rdp->gpnum, rdp->passed_quiesc, rdp->passed_quiesc_completed, - rdp->qs_pending, - rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending, - (int)(rdp->n_rcu_pending & 0xffff)); + rdp->qs_pending); #ifdef CONFIG_NO_HZ seq_printf(m, " dt=%d/%d dn=%d df=%lu", rdp->dynticks->dynticks, @@ -102,14 +100,12 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) return; - seq_printf(m, "%d,%s,%ld,%ld,%d,%ld,%d,%ld,%ld", + seq_printf(m, "%d,%s,%ld,%ld,%d,%ld,%d", rdp->cpu, cpu_is_offline(rdp->cpu) ? "\"Y\"" : "\"N\"", rdp->completed, rdp->gpnum, rdp->passed_quiesc, rdp->passed_quiesc_completed, - rdp->qs_pending, - rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending, - rdp->n_rcu_pending); + rdp->qs_pending); #ifdef CONFIG_NO_HZ seq_printf(m, ",%d,%d,%d,%lu", rdp->dynticks->dynticks, @@ -123,7 +119,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) static int show_rcudata_csv(struct seq_file *m, void *unused) { - seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\",\"rpfq\",\"rp\","); + seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\","); #ifdef CONFIG_NO_HZ seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\","); #endif /* #ifdef CONFIG_NO_HZ */ -- cgit v1.2.3-70-g09d2