[PATCH 6/6] Export per cpu hardirq and softirq time in proc

[Venkatesh Pallipadi]

I can predict this change being debated.

There is already per CPU and system level irq time in /proc/stat, which
on arch like x86 is based on sampled data. Earlier patch adds a fine
grained irq time option for such archs. And exporting this fine grained
irq time to userspace seems helpful.

How should it be exported though? I considered:
(1) Changing the currently exported info in /proc/stat. Doing that though will
    likely break the sum view to the user as user/system/ and other times there
    are still sample based and only irq time will be fine grained. So, user may
    see sum time != 100% in top etc.
(2) Add a new interface in /proc. Implied an additional file read and buffer
    allocation, etc which I want to avoid if possible.
(3) Don't export this info at all. I am ok with this as a alternative. But,
    I needed this to be exported somewhere for my testing atleast.
(4) piggyback on /proc/interrupts and /proc/softirqs. Assuming users interested
    in this kind of info are already looking into those files, we wont have
    overhead of additional file read. There is still a likely hood of breaking
    some apps which only expect interrupt count in those files. But, this seemed
    a good option to me.

So, here is the patch that does (4)

Signed-off-by: Venkatesh Pallipadi <venki@xxxxxxxxxx>
---
 Documentation/filesystems/proc.txt |    9 +++++++++
 fs/proc/interrupts.c               |   11 ++++++++++-
 fs/proc/softirqs.c                 |    8 ++++++++
 include/linux/sched.h              |    3 +++
 kernel/sched.c                     |   27 +++++++++++++++++++++++++++
 5 files changed, 57 insertions(+), 1 deletions(-)

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index a6aca87..4456011 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -536,6 +536,11 @@ the threshold vector does not exist on x86_64 platforms.  Others are
 suppressed when the system is a uniprocessor.  As of this writing, only
 i386 and x86_64 platforms support the new IRQ vector displays.
 
+Another addition to /proc/interrupt is "Time:" line at the end which
+displays time spent by corresponding CPU processing interrupts in USER_HZ units.
+This time is based on fine grained accouting when CONFIG_VIRT_CPU_ACCOUNTING
+or CONFIG_IRQ_TIME_ACCOUNTING is active, otherwise it is tick sample based.
+
 Of some interest is the introduction of the /proc/irq directory to 2.4.
 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
@@ -824,6 +829,10 @@ Provides counts of softirq handlers serviced since boot time, for each cpu.
  HRTIMER:          0          0          0          0
      RCU:       1678       1769       2178       2250
 
+Addition to /proc/softirqs is "Time:" line at the end which
+displays time spent by corresponding CPU processing softirqs in USER_HZ units.
+This time is based on fine grained accouting when CONFIG_VIRT_CPU_ACCOUNTING
+or CONFIG_IRQ_TIME_ACCOUNTING is active, otherwise it is tick sample based.
 
 1.3 IDE devices in /proc/ide
 ----------------------------
diff --git a/fs/proc/interrupts.c b/fs/proc/interrupts.c
index 05029c0..66d913a 100644
--- a/fs/proc/interrupts.c
+++ b/fs/proc/interrupts.c
@@ -3,6 +3,7 @@
 #include <linux/interrupt.h>
 #include <linux/irqnr.h>
 #include <linux/proc_fs.h>
+#include <linux/sched.h>
 #include <linux/seq_file.h>
 
 /*
@@ -23,7 +24,15 @@ static void *int_seq_next(struct seq_file *f, void *v, loff_t *pos)
 
 static void int_seq_stop(struct seq_file *f, void *v)
 {
-	/* Nothing to do */
+	int j;
+
+	seq_printf(f, "\n");
+	seq_printf(f, "Time:");
+	for_each_possible_cpu(j)
+		seq_printf(f, " %10lu", (unsigned long)get_cpu_hardirq_time(j));
+	seq_printf(f, "  Interrupt Processing Time\n");
+	seq_printf(f, "\n");
+
 }
 
 static const struct seq_operations int_seq_ops = {
diff --git a/fs/proc/softirqs.c b/fs/proc/softirqs.c
index 1807c24..f028329 100644
--- a/fs/proc/softirqs.c
+++ b/fs/proc/softirqs.c
@@ -1,6 +1,7 @@
 #include <linux/init.h>
 #include <linux/kernel_stat.h>
 #include <linux/proc_fs.h>
+#include <linux/sched.h>
 #include <linux/seq_file.h>
 
 /*
@@ -21,6 +22,13 @@ static int show_softirqs(struct seq_file *p, void *v)
 			seq_printf(p, " %10u", kstat_softirqs_cpu(i, j));
 		seq_printf(p, "\n");
 	}
+
+	seq_printf(p, "\n");
+	seq_printf(p, "    Time:");
+	for_each_possible_cpu(j)
+		seq_printf(p, " %10lu", (unsigned long)get_cpu_softirq_time(j));
+	seq_printf(p, "\n");
+
 	return 0;
 }
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dbb6808..9033b21 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1826,6 +1826,9 @@ extern void sched_clock_idle_sleep_event(void);
 extern void sched_clock_idle_wakeup_event(u64 delta_ns);
 #endif
 
+extern clock_t get_cpu_hardirq_time(int cpu);
+extern clock_t get_cpu_softirq_time(int cpu);
+
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 /*
  * An i/f to runtime opt-in for irq time accounting based off of sched_clock.
diff --git a/kernel/sched.c b/kernel/sched.c
index 8ac5389..de63d2e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -73,6 +73,7 @@
 #include <linux/ftrace.h>
 #include <linux/slab.h>
 
+#include <asm/cputime.h>
 #include <asm/tlb.h>
 #include <asm/irq_regs.h>
 
@@ -2037,6 +2038,22 @@ static void sched_irq_power_update_fair(int cpu, struct cfs_rq *cfs_rq,
 	}
 }
 
+clock_t get_cpu_hardirq_time(int cpu)
+{
+	if (!sched_clock_irqtime)
+		return cputime64_to_clock_t(kstat_cpu(cpu).cpustat.irq);
+
+	return nsec_to_clock_t(per_cpu(cpu_hardirq_time,(cpu)));
+}
+
+clock_t get_cpu_softirq_time(int cpu)
+{
+	if (!sched_clock_irqtime)
+		return cputime64_to_clock_t(kstat_cpu(cpu).cpustat.softirq);
+
+	return nsec_to_clock_t(per_cpu(cpu_softirq_time,(cpu)));
+}
+
 #else
 
 #define update_irq_time(cpu, crq)		do { } while (0)
@@ -2056,6 +2073,16 @@ static u64 unaccount_irq_delta_rt(u64 delta_exec, int cpu, struct rt_rq *rt_rq)
 
 #define sched_irq_power_update_fair(cpu, crq, rq)	do { } while (0)
 
+clock_t get_cpu_hardirq_time(int cpu)
+{
+	return cputime64_to_clock_t(kstat_cpu(cpu).cpustat.irq);
+}
+
+clock_t get_cpu_softirq_time(int cpu)
+{
+	return cputime64_to_clock_t(kstat_cpu(cpu).cpustat.softirq);
+}
+
 #endif
 
 #include "sched_idletask.c"
-- 
1.7.1

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