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Subject[RFC][PATCH] cutting up struct kernel_stat into cpu_stat
The attached patch-in-progress removes the per-cpu statistics from
struct kernel_stat and puts them in a cpu_stat structure, one per cpu,
cacheline padded. The data is still coolated and presented through
/proc/stat, but another file /proc/cpustat is also added. The locking
is as nonexistant as it was with kernel_stat, but who cares, they're
just fuzzy stats to be eyeballed by system tuners :).

A tool for printing the cpu stats specifically can be found near:

http://www.osdlab.org/sw_resources/cpustat/index.shtml

Its output is almost identical to solaris' mpstat.

I'm not sure I like the macro use, but it shields the callers from the
union garbage. We can easily also make a THIS_CPU_STAT_ADD() interface,
as some have hinted would be nice :)

Currently its mostly ( :) ) only collecting the stats that were
collected in kernel_stat. I'd like to add more stats -- page faults,
syscalls, cross-cpu calls, etc. I understand people not wanting more
live cachelines in the fast paths. I can make CPU_CRITICAL_STAT defines
that are config-ed out..

comments? If its ok I can whip up a patch that updates all the ports
use of ->irqs[] as well.

- z
[ heading out for lunch :) ]
--- linux-2.4.5-cpustat/fs/proc/proc_misc.c.cpustat Fri Apr 13 20:26:07 2001
+++ linux-2.4.5-cpustat/fs/proc/proc_misc.c Thu Jun 21 12:23:49 2001
@@ -265,32 +265,36 @@
int i, len;
extern unsigned long total_forks;
unsigned long jif = jiffies;
- unsigned int sum = 0, user = 0, nice = 0, system = 0;
+ unsigned int sum = 0, user = 0, nice = 0, system = 0, ctxt = 0;
int major, disk;

for (i = 0 ; i < smp_num_cpus; i++) {
int cpu = cpu_logical_map(i), j;

- user += kstat.per_cpu_user[cpu];
- nice += kstat.per_cpu_nice[cpu];
- system += kstat.per_cpu_system[cpu];
+ user += CPU_STAT_VAL(cpu, user);
+ nice += CPU_STAT_VAL(cpu, nice);
+ system += CPU_STAT_VAL(cpu, system);
+ ctxt += CPU_STAT_VAL(cpu, context_swtch);
#if !defined(CONFIG_ARCH_S390)
for (j = 0 ; j < NR_IRQS ; j++)
- sum += kstat.irqs[cpu][j];
+ sum += CPU_STAT_VAL(cpu, irqs[j]);
#endif
}

len = sprintf(page, "cpu %u %u %u %lu\n", user, nice, system,
jif * smp_num_cpus - (user + nice + system));
- for (i = 0 ; i < smp_num_cpus; i++)
+ for (i = 0 ; i < smp_num_cpus; i++) {
+ unsigned int user_i, nice_i, system_i;
+
+ user_i = CPU_STAT_VAL(cpu_logical_map(i), user);
+ nice_i = CPU_STAT_VAL(cpu_logical_map(i), nice);
+ system_i = CPU_STAT_VAL(cpu_logical_map(i), system);
+
len += sprintf(page + len, "cpu%d %u %u %u %lu\n",
i,
- kstat.per_cpu_user[cpu_logical_map(i)],
- kstat.per_cpu_nice[cpu_logical_map(i)],
- kstat.per_cpu_system[cpu_logical_map(i)],
- jif - ( kstat.per_cpu_user[cpu_logical_map(i)] \
- + kstat.per_cpu_nice[cpu_logical_map(i)] \
- + kstat.per_cpu_system[cpu_logical_map(i)]));
+ user_i, nice_i, system_i,
+ jif - ( user_i + nice_i + system_i ) );
+ }
len += sprintf(page + len,
"page %u %u\n"
"swap %u %u\n"
@@ -330,13 +334,58 @@
"\nctxt %u\n"
"btime %lu\n"
"processes %lu\n",
- kstat.context_swtch,
+ ctxt,
xtime.tv_sec - jif / HZ,
total_forks);

return proc_calc_metrics(page, start, off, count, eof, len);
}

+static int cstat_read_proc(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int i, len;
+
+ len = sprintf(page, "cpu_stat 0.0\n");
+
+ for (i = 0 ; i < smp_num_cpus; i++) {
+ unsigned int user, nice, system;
+ int j, cpu = cpu_logical_map(i);
+
+#if !defined(CONFIG_ARCH_S390)
+ len += sprintf(page + len, "cpu%d irqs ", cpu);
+ for (j = 0 ; j < NR_IRQS ; j++) {
+ len += sprintf(page + len, " %u",
+ CPU_STAT_VAL(cpu, irqs[j]));
+ }
+ len += sprintf(page + len, "\n");
+#endif
+#if defined(CONFIG_SMP)
+ len += sprintf(page + len, "cpu%d context_migration %u\n",
+ cpu, CPU_STAT_VAL(cpu, context_migration));
+#endif
+ len += sprintf(page + len, "cpu%d bottom_halves %u\n",
+ cpu, CPU_STAT_VAL(cpu, bh));
+ len += sprintf(page + len, "cpu%d context_switches %u\n",
+ cpu, CPU_STAT_VAL(cpu, context_swtch));
+
+ user = CPU_STAT_VAL(cpu_logical_map(i), user);
+ nice = CPU_STAT_VAL(cpu_logical_map(i), nice);
+ system = CPU_STAT_VAL(cpu_logical_map(i), system);
+
+ len += sprintf(page + len, "cpu%d user_time %u\n",
+ cpu, user);
+ len += sprintf(page + len, "cpu%d nice_time %u\n",
+ cpu, nice);
+ len += sprintf(page + len, "cpu%d system_time %u\n",
+ cpu, system);
+ len += sprintf(page + len, "cpu%d unaccounted_time %u\n",
+ cpu, jiffies - ( user + nice + system ) );
+ }
+
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
static int devices_read_proc(char *page, char **start, off_t off,
int count, int *eof, void *data)
{
@@ -532,6 +581,7 @@
{"ksyms", ksyms_read_proc},
#endif
{"stat", kstat_read_proc},
+ {"cpustat", cstat_read_proc},
{"devices", devices_read_proc},
{"partitions", partitions_read_proc},
#if !defined(CONFIG_ARCH_S390)
--- linux-2.4.5-cpustat/kernel/sched.c.cpustat Fri Apr 20 18:26:16 2001
+++ linux-2.4.5-cpustat/kernel/sched.c Thu Jun 21 12:01:34 2001
@@ -107,6 +107,8 @@

struct kernel_stat kstat;

+union cpu_stat_u cpu_stats[NR_CPUS] __cacheline_aligned = { {{0, }}};
+
#ifdef CONFIG_SMP

#define idle_task(cpu) (init_tasks[cpu_number_map(cpu)])
@@ -607,6 +609,7 @@
sched_data->curr = next;
#ifdef CONFIG_SMP
next->has_cpu = 1;
+ CPU_STAT_ADD(this_cpu, context_migration, next->processor != this_cpu );
next->processor = this_cpu;
#endif
spin_unlock_irq(&runqueue_lock);
@@ -632,7 +635,7 @@

#endif /* CONFIG_SMP */

- kstat.context_swtch++;
+ CPU_STAT_ADD(this_cpu, context_swtch, 1);
/*
* there are 3 processes which are affected by a context switch:
*
--- linux-2.4.5-cpustat/kernel/timer.c.cpustat Sun Dec 10 09:53:19 2000
+++ linux-2.4.5-cpustat/kernel/timer.c Wed Jun 20 13:45:06 2001
@@ -588,12 +588,12 @@
p->need_resched = 1;
}
if (p->nice > 0)
- kstat.per_cpu_nice[cpu] += user_tick;
+ CPU_STAT_ADD(cpu, nice, user_tick);
else
- kstat.per_cpu_user[cpu] += user_tick;
- kstat.per_cpu_system[cpu] += system;
+ CPU_STAT_ADD(cpu, user, user_tick);
+ CPU_STAT_ADD(cpu, system, system);
} else if (local_bh_count(cpu) || local_irq_count(cpu) > 1)
- kstat.per_cpu_system[cpu] += system;
+ CPU_STAT_ADD(cpu, system, system);
}

/*
--- linux-2.4.5-cpustat/kernel/softirq.c.cpustat Fri Dec 29 14:07:24 2000
+++ linux-2.4.5-cpustat/kernel/softirq.c Thu Jun 21 11:29:01 2001
@@ -74,7 +74,7 @@
mask &= ~active;

do {
- if (active & 1)
+ if (active & 1)
h->action(h);
h++;
active >>= 1;
@@ -253,8 +253,10 @@
if (!hardirq_trylock(cpu))
goto resched_unlock;

- if (bh_base[nr])
+ if (bh_base[nr]) {
bh_base[nr]();
+ CPU_STAT_ADD(cpu, bh, 1);
+ }

hardirq_endlock(cpu);
spin_unlock(&global_bh_lock);
--- linux-2.4.5-cpustat/include/linux/kernel_stat.h.cpustat Fri May 25 18:01:27 2001
+++ linux-2.4.5-cpustat/include/linux/kernel_stat.h Thu Jun 21 11:28:52 2001
@@ -16,9 +16,6 @@
#define DK_MAX_DISK 16

struct kernel_stat {
- unsigned int per_cpu_user[NR_CPUS],
- per_cpu_nice[NR_CPUS],
- per_cpu_system[NR_CPUS];
unsigned int dk_drive[DK_MAX_MAJOR][DK_MAX_DISK];
unsigned int dk_drive_rio[DK_MAX_MAJOR][DK_MAX_DISK];
unsigned int dk_drive_wio[DK_MAX_MAJOR][DK_MAX_DISK];
@@ -26,17 +23,33 @@
unsigned int dk_drive_wblk[DK_MAX_MAJOR][DK_MAX_DISK];
unsigned int pgpgin, pgpgout;
unsigned int pswpin, pswpout;
-#if !defined(CONFIG_ARCH_S390)
- unsigned int irqs[NR_CPUS][NR_IRQS];
-#endif
unsigned int ipackets, opackets;
unsigned int ierrors, oerrors;
unsigned int collisions;
- unsigned int context_swtch;
};

extern struct kernel_stat kstat;

+union cpu_stat_u {
+ struct cpu_stat {
+ unsigned int user, nice, system;
+ unsigned int context_swtch;
+ unsigned int bh;
+#if defined(CONFIG_SMP)
+ unsigned int context_migration;
+#endif
+#if !defined(CONFIG_ARCH_S390)
+ unsigned int irqs[NR_IRQS];
+#endif
+ } cs;
+ char __pad [SMP_CACHE_BYTES];
+};
+
+extern union cpu_stat_u cpu_stats[NR_CPUS];
+
+#define CPU_STAT_ADD(CPU, STAT, VAL) cpu_stats[CPU].cs.STAT += VAL
+#define CPU_STAT_VAL(CPU, STAT) cpu_stats[CPU].cs.STAT
+
#if !defined(CONFIG_ARCH_S390)
/*
* Number of interrupts per specific IRQ source, since bootup
@@ -46,7 +59,7 @@
int i, sum=0;

for (i = 0 ; i < smp_num_cpus ; i++)
- sum += kstat.irqs[cpu_logical_map(i)][irq];
+ sum += CPU_STAT_VAL(cpu_logical_map(i), irqs[irq]);

return sum;
}
--- linux-2.4.5-cpustat/arch/i386/kernel/irq.c.cpustat Fri Feb 9 11:29:44 2001
+++ linux-2.4.5-cpustat/arch/i386/kernel/irq.c Wed Jun 20 14:02:34 2001
@@ -146,7 +146,7 @@
#else
for (j = 0; j < smp_num_cpus; j++)
p += sprintf(p, "%10u ",
- kstat.irqs[cpu_logical_map(j)][i]);
+ CPU_STAT_VAL(cpu_logical_map(j), irqs[i]));
#endif
p += sprintf(p, " %14s", irq_desc[i].handler->typename);
p += sprintf(p, " %s", action->name);
@@ -564,7 +564,7 @@
struct irqaction * action;
unsigned int status;

- kstat.irqs[cpu][irq]++;
+ CPU_STAT_ADD(cpu, irqs[irq], 1);
spin_lock(&desc->lock);
desc->handler->ack(irq);
/*
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