Greg, Ben,
Can you add this commit to the stable branches. Without it, the
migration thread's accounting is just totally screwed up:
By running a simple shell while loop along with a ps loop, top shows:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
17 root RT 0 0 0 0 S 9999.0 0.0 9:27.50 migration/3
13 root RT 0 0 0 0 S 128.2 0.0 9:50.23 migration/2
2805 root 20 0 105m 1904 1416 S 13.9 0.1 0:06.69 bash
4090 root 20 0 105m 1904 1416 S 2.0 0.1 0:00.90 bash
2773 root 20 0 85484 3372 2620 S 0.3 0.2 0:00.03 sshd
For 3.4, the commit can be directly cherry picked:
commit 8f6189684eb4e85e6c593cd710693f09c944450a
Author: Mike Galbraith <mgalbra...@suse.de>
Date: Sat Aug 4 05:44:14 2012 +0200
sched: Fix migration thread runtime bogosity
Below is a backport for 3.2.
Thanks!
-- Steve
From 8f6189684eb4e85e6c593cd710693f09c944450a Mon Sep 17 00:00:00 2001
From: Mike Galbraith <mgalbra...@suse.de>
Date: Sat, 4 Aug 2012 05:44:14 +0200
Subject: [PATCH] sched: Fix migration thread runtime bogosity
Make stop scheduler class do the same accounting as other classes,
Migration threads can be caught in the act while doing exec balancing,
leading to the below due to use of unmaintained ->se.exec_start. The
load that triggered this particular instance was an apparently out of
control heavily threaded application that does system monitoring in
what equated to an exec bomb, with one of the VERY frequently migrated
tasks being ps.
%CPU PID USER CMD
99.3 45 root [migration/10]
97.7 53 root [migration/12]
97.0 57 root [migration/13]
90.1 49 root [migration/11]
89.6 65 root [migration/15]
88.7 17 root [migration/3]
80.4 37 root [migration/8]
78.1 41 root [migration/9]
44.2 13 root [migration/2]
Signed-off-by: Mike Galbraith <mgalbra...@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
Link: http://lkml.kernel.org/r/1344051854.6739.19.ca...@marge.simpson.net
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
kernel/sched_stoptask.c | 22 +++++++++++++++++++++-
1 files changed, 21 insertions(+), 1 deletions(-)
Index: linux-trace.git/kernel/sched_stoptask.c
===================================================================
--- linux-trace.git.orig/kernel/sched_stoptask.c
+++ linux-trace.git/kernel/sched_stoptask.c
@@ -25,8 +25,10 @@ static struct task_struct *pick_next_tas
{
struct task_struct *stop = rq->stop;
- if (stop && stop->on_rq)
+ if (stop && stop->on_rq) {
+ stop->se.exec_start = rq->clock_task;
return stop;
+ }
return NULL;
}
@@ -50,6 +52,21 @@ static void yield_task_stop(struct rq *r
static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
{
+ struct task_struct *curr = rq->curr;
+ u64 delta_exec;
+
+ delta_exec = rq->clock_task - curr->se.exec_start;
+ if (unlikely((s64)delta_exec < 0))
+ delta_exec = 0;
+
+ schedstat_set(curr->se.statistics.exec_max,
+ max(curr->se.statistics.exec_max, delta_exec));
+
+ curr->se.sum_exec_runtime += delta_exec;
+ account_group_exec_runtime(curr, delta_exec);
+
+ curr->se.exec_start = rq->clock_task;
+ cpuacct_charge(curr, delta_exec);
}
static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
@@ -58,6 +75,9 @@ static void task_tick_stop(struct rq *rq
static void set_curr_task_stop(struct rq *rq)
{
+ struct task_struct *stop = rq->stop;
+
+ stop->se.exec_start = rq->clock_task;
}
static void switched_to_stop(struct rq *rq, struct task_struct *p)
--
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