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Message-Id: <1292980144-28796-2-git-send-email-venki@google.com>
Date: Tue, 21 Dec 2010 17:09:00 -0800
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>,
Eric Dumazet <eric.dumazet@...il.com>,
Shaun Ruffell <sruffell@...ium.com>,
Venkatesh Pallipadi <venki@...gle.com>
Subject: [PATCH 1/5] Free up pf flag PF_KSOFTIRQD -v2
Patchset:
This is Part 2 of
"Proper kernel irq time accounting -v4"
http://lkml.indiana.edu/hypermail//linux/kernel/1010.0/01175.html
and applies 2.6.37-rc7.
Part 1 solves the way irqs are accounted in scheduler and tasks. This
patchset solves how irq times are reported in /proc/stat and also not
to include irq time in task->stime, etc.
Example:
Running a cpu intensive loop and network intensive nc on a 4 CPU system
and looking at 'top' output.
With vanilla kernel:
Cpu0 : 0.0% us, 0.3% sy, 0.0% ni, 99.3% id, 0.0% wa, 0.0% hi, 0.3% si
Cpu1 : 100.0% us, 0.0% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu2 : 1.3% us, 27.2% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi, 71.4% si
Cpu3 : 1.6% us, 1.3% sy, 0.0% ni, 96.7% id, 0.0% wa, 0.0% hi, 0.3% si
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
7555 root 20 0 1760 528 436 R 100 0.0 0:15.79 nc
7563 root 20 0 3632 268 204 R 100 0.0 0:13.13 loop
Notes:
* Both tasks show 100% CPU, even when one of them is stuck on a CPU thats
processing 70% softirq.
* no hardirq time.
With "Part 1" patches:
Cpu0 : 0.0% us, 0.0% sy, 0.0% ni, 100.0% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu1 : 100.0% us, 0.0% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi, 0.0% si
Cpu2 : 2.0% us, 30.6% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi, 67.4% si
Cpu3 : 0.7% us, 0.7% sy, 0.3% ni, 98.3% id, 0.0% wa, 0.0% hi, 0.0% si
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
6289 root 20 0 3632 268 204 R 100 0.0 2:18.67 loop
5737 root 20 0 1760 528 436 R 33 0.0 0:26.72 nc
Notes:
* Tasks show 100% CPU and 33% CPU that correspond to their non-irq exec time.
* no hardirq time.
With "Part 1 + Part 2" patches:
Cpu0 : 1.3% us, 1.0% sy, 0.3% ni, 97.0% id, 0.0% wa, 0.0% hi, 0.3% si
Cpu1 : 99.3% us, 0.0% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.7% hi, 0.0% si
Cpu2 : 1.3% us, 31.5% sy, 0.0% ni, 0.0% id, 0.0% wa, 8.3% hi, 58.9% si
Cpu3 : 1.0% us, 2.0% sy, 0.3% ni, 95.0% id, 0.0% wa, 0.7% hi, 1.0% si
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20929 root 20 0 3632 268 204 R 99 0.0 3:48.25 loop
20796 root 20 0 1760 528 436 R 33 0.0 2:38.65 nc
Notes:
* Both task exec time and hard irq time reported correctly.
* hi and si time are based on fine granularity info and not on samples.
* getrusage would give proper utime/stime split not including irq times
in that ratio.
* Other places that report user/sys time like, cgroup cpuacct.stat will
now include only non-irq exectime.
This patch:
Cleanup patch, freeing up PF_KSOFTIRQD and use per_cpu ksoftirqd pointer
instead, as suggested by Eric Dumazet.
Tested-by: Shaun Ruffell <sruffell@...ium.com>
Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
---
include/linux/interrupt.h | 7 +++++++
include/linux/sched.h | 1 -
kernel/sched.c | 2 +-
kernel/softirq.c | 3 +--
4 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 79d0c4f..3802fac 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -426,6 +426,13 @@ extern void raise_softirq(unsigned int nr);
*/
DECLARE_PER_CPU(struct list_head [NR_SOFTIRQS], softirq_work_list);
+DECLARE_PER_CPU(struct task_struct *, ksoftirqd);
+
+static inline struct task_struct *this_cpu_ksoftirqd(void)
+{
+ return this_cpu_read(ksoftirqd);
+}
+
/* Try to send a softirq to a remote cpu. If this cannot be done, the
* work will be queued to the local cpu.
*/
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2238745..86924ff 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1699,7 +1699,6 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
/*
* Per process flags
*/
-#define PF_KSOFTIRQD 0x00000001 /* I am ksoftirqd */
#define PF_STARTING 0x00000002 /* being created */
#define PF_EXITING 0x00000004 /* getting shut down */
#define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */
diff --git a/kernel/sched.c b/kernel/sched.c
index 297d1a0..bfc9646 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2011,7 +2011,7 @@ void account_system_vtime(struct task_struct *curr)
*/
if (hardirq_count())
__this_cpu_add(cpu_hardirq_time, delta);
- else if (in_serving_softirq() && !(curr->flags & PF_KSOFTIRQD))
+ else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
__this_cpu_add(cpu_softirq_time, delta);
irq_time_write_end();
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 18f4be0..b904be8 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -54,7 +54,7 @@ EXPORT_SYMBOL(irq_stat);
static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
-static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
+DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
char *softirq_to_name[NR_SOFTIRQS] = {
"HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
@@ -721,7 +721,6 @@ static int run_ksoftirqd(void * __bind_cpu)
{
set_current_state(TASK_INTERRUPTIBLE);
- current->flags |= PF_KSOFTIRQD;
while (!kthread_should_stop()) {
preempt_disable();
if (!local_softirq_pending()) {
--
1.7.3.1
--
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