From Dipankar
This patch makes some basic statistics for RCU available in /proc/rcu.
It is a trimmed down version of the earler rcu_stats patch in -mm kernels.
I removed all the RCU implementation dependent stats (mostly needed for
debugging) and retained only the part that was very generic in
nature - # of RCU requests and # of actual RCU updates for each
CPU. This will allow us to monitor the health of the RCU
subsystem and such things have been extremely useful for me to
investigate problems.
[dipankar@llm04 dipankar]$ cat /proc/rcu
CPU : 0
RCU requests : 0
RCU updates : 0
CPU : 1
RCU requests : 0
RCU updates : 0
CPU : 2
RCU requests : 0
RCU updates : 0
CPU : 3
RCU requests : 0
RCU updates : 0
25-akpm/Documentation/filesystems/proc.txt | 4 ++
25-akpm/fs/proc/proc_misc.c | 13 +++++++
25-akpm/include/linux/rcupdate.h | 4 ++
25-akpm/kernel/rcupdate.c | 48 +++++++++++++++++++++++++++--
4 files changed, 67 insertions(+), 2 deletions(-)
diff -puN fs/proc/proc_misc.c~rcu-stats fs/proc/proc_misc.c
--- 25/fs/proc/proc_misc.c~rcu-stats Tue Mar 18 15:07:32 2003
+++ 25-akpm/fs/proc/proc_misc.c Tue Mar 18 15:07:32 2003
@@ -246,6 +246,18 @@ static struct file_operations proc_cpuin
.release = seq_release,
};
+extern struct seq_operations rcu_op;
+static int rcu_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &rcu_op);
+}
+static struct file_operations proc_rcu_operations = {
+ .open = rcu_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
extern struct seq_operations vmstat_op;
static int vmstat_open(struct inode *inode, struct file *file)
{
@@ -592,6 +604,7 @@ void __init proc_misc_init(void)
if (entry)
entry->proc_fops = &proc_kmsg_operations;
create_seq_entry("cpuinfo", 0, &proc_cpuinfo_operations);
+ create_seq_entry("rcu", 0, &proc_rcu_operations);
create_seq_entry("partitions", 0, &proc_partitions_operations);
#if !defined(CONFIG_ARCH_S390)
create_seq_entry("interrupts", 0, &proc_interrupts_operations);
diff -puN include/linux/rcupdate.h~rcu-stats include/linux/rcupdate.h
--- 25/include/linux/rcupdate.h~rcu-stats Tue Mar 18 15:07:32 2003
+++ 25-akpm/include/linux/rcupdate.h Tue Mar 18 15:07:32 2003
@@ -95,6 +95,8 @@ struct rcu_data {
long batch; /* Batch # for current RCU batch */
struct list_head nxtlist;
struct list_head curlist;
+ long nr_rcureqs;
+ long nr_rcupdates;
};
DECLARE_PER_CPU(struct rcu_data, rcu_data);
@@ -105,6 +107,8 @@ extern struct rcu_ctrlblk rcu_ctrlblk;
#define RCU_batch(cpu) (per_cpu(rcu_data, (cpu)).batch)
#define RCU_nxtlist(cpu) (per_cpu(rcu_data, (cpu)).nxtlist)
#define RCU_curlist(cpu) (per_cpu(rcu_data, (cpu)).curlist)
+#define RCU_nr_rcureqs(cpu) (per_cpu(rcu_data, (cpu)).nr_rcureqs)
+#define RCU_nr_rcupdates(cpu) (per_cpu(rcu_data, (cpu)).nr_rcupdates)
#define RCU_QSCTR_INVALID 0
diff -puN kernel/rcupdate.c~rcu-stats kernel/rcupdate.c
--- 25/kernel/rcupdate.c~rcu-stats Tue Mar 18 15:07:32 2003
+++ 25-akpm/kernel/rcupdate.c Tue Mar 18 15:07:32 2003
@@ -41,6 +41,7 @@
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/percpu.h>
+#include <linux/seq_file.h>
#include <linux/notifier.h>
#include <linux/rcupdate.h>
@@ -75,6 +76,7 @@ void call_rcu(struct rcu_head *head, voi
local_irq_save(flags);
cpu = smp_processor_id();
list_add_tail(&head->list, &RCU_nxtlist(cpu));
+ RCU_nr_rcureqs(cpu)++;
local_irq_restore(flags);
}
@@ -82,7 +84,7 @@ void call_rcu(struct rcu_head *head, voi
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
-static void rcu_do_batch(struct list_head *list)
+static void rcu_do_batch(int cpu, struct list_head *list)
{
struct list_head *entry;
struct rcu_head *head;
@@ -92,6 +94,7 @@ static void rcu_do_batch(struct list_hea
list_del(entry);
head = list_entry(entry, struct rcu_head, list);
head->func(head->arg);
+ RCU_nr_rcupdates(cpu)++;
}
}
@@ -187,7 +190,7 @@ static void rcu_process_callbacks(unsign
}
rcu_check_quiescent_state();
if (!list_empty(&list))
- rcu_do_batch(&list);
+ rcu_do_batch(cpu, &list);
}
void rcu_check_callbacks(int cpu, int user)
@@ -266,3 +269,44 @@ void synchronize_kernel(void)
EXPORT_SYMBOL(call_rcu);
EXPORT_SYMBOL(synchronize_kernel);
+
+#ifdef CONFIG_PROC_FS
+
+static void *rcu_start(struct seq_file *m, loff_t *pos)
+{
+ static int cpu;
+ cpu = *pos;
+ return *pos < NR_CPUS ? &cpu : NULL;
+}
+
+static void *rcu_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ ++*pos;
+ return rcu_start(m, pos);
+}
+
+static void rcu_stop(struct seq_file *m, void *v)
+{
+}
+
+static int show_rcu(struct seq_file *m, void *v)
+{
+ int cpu = *(int *)v;
+
+ if (!cpu_online(cpu))
+ return 0;
+ seq_printf(m, "CPU : %d\n", cpu);
+ seq_printf(m, "RCU requests : %ld\n", RCU_nr_rcureqs(cpu));
+ seq_printf(m, "RCU updates : %ld\n\n", RCU_nr_rcupdates(cpu));
+ return 0;
+}
+
+struct seq_operations rcu_op = {
+ .start = rcu_start,
+ .next = rcu_next,
+ .stop = rcu_stop,
+ .show = show_rcu,
+};
+
+#endif
+
diff -puN Documentation/filesystems/proc.txt~rcu-stats Documentation/filesystems/proc.txt
--- 25/Documentation/filesystems/proc.txt~rcu-stats Tue Mar 18 15:07:32 2003
+++ 25-akpm/Documentation/filesystems/proc.txt Tue Mar 18 15:07:32 2003
@@ -222,6 +222,7 @@ Table 1-3: Kernel info in /proc
partitions Table of partitions known to the system
pci Depreciated info of PCI bus (new way -> /proc/bus/pci/,
decoupled by lspci (2.4)
+ rcu Read-Copy Update information (2.5)
rtc Real time clock
scsi SCSI info (see text)
slabinfo Slab pool info
@@ -346,6 +347,9 @@ available. In this case, there are 0 ch
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
+The rcu file gives information about Read-Copy Update synchronization
+primitive. It indicates the number for RCU requests and actual
+updates for every CPU.
1.3 IDE devices in /proc/ide
----------------------------
_