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Date: Thu, 16 Sep 2010 18:56:36 -0700
From: Venkatesh Pallipadi <venki@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
Venkatesh Pallipadi <venki@...gle.com>
Subject: [PATCH 6/6] Export per cpu hardirq and softirq time in proc
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@...gle.com>
---
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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