From 8f6189684eb4e85e6c593cd710693f09c944450a Mon Sep 17 00:00:00 2001 From: Mike Galbraith 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 Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1344051854.6739.19.camel@marge.simpson.net Signed-off-by: Thomas Gleixner --- kernel/sched/stop_task.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index 7b386e8..da5eb5b 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -27,8 +27,10 @@ static struct task_struct *pick_next_task_stop(struct rq *rq) { 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; } @@ -52,6 +54,21 @@ static void yield_task_stop(struct rq *rq) 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) @@ -60,6 +77,9 @@ static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued) 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) -- 2.7.4