Messages in this thread | | | Date | Thu, 16 Apr 2020 11:35:02 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] sched/cpuacct: Fix charge cpuacct.usage_sys incorrently. |
| |
On Thu, 16 Apr 2020 22:18:33 +0800 Muchun Song <songmuchun@bytedance.com> wrote:
> The user_mode(task_pt_regs(tsk)) always return true for > user thread, and false for kernel thread. So it means that > the cpuacct.usage_sys is the time that kernel thread uses > not the time that thread uses in the kernel mode. We can > use get_irq_regs() instead of task_pt_regs() to fix it. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > kernel/sched/cpuacct.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c > index 6448b0438ffb2..edfc62554648e 100644 > --- a/kernel/sched/cpuacct.c > +++ b/kernel/sched/cpuacct.c > @@ -5,6 +5,7 @@ > * Based on the work by Paul Menage (menage@google.com) and Balbir Singh > * (balbir@in.ibm.com). > */ > +#include <asm/irq_regs.h> > #include "sched.h" > > /* Time spent by the tasks of the CPU accounting group executing in ... */ > @@ -339,7 +340,7 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime) > { > struct cpuacct *ca; > int index = CPUACCT_STAT_SYSTEM; > - struct pt_regs *regs = task_pt_regs(tsk); > + struct pt_regs *regs = get_irq_regs();
But get_irq_regs() is only available from interrupt context. This will be NULL most the time, whereas the original way will have regs existing for the task.
> > if (regs && user_mode(regs)) > index = CPUACCT_STAT_USER;
To show this, I applied your patch then did the following:
# echo 'p:cpuacct cpuacct_charge+0x36 regs=%ax' > /sys/kernel/tracing/kprobe_events
Where I found that the test of 'regs' is %rax at offset 0x36.
# trace-cmd start -p function -l cpuacct_charge -e kprobes # trace-cmd show # tracer: function # # entries-in-buffer/entries-written: 70664/70664 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | <...>-1720 [002] d..2 306.430302: cpuacct_charge <-update_curr <...>-1720 [002] d..3 306.430306: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 <...>-1720 [002] dN.2 306.430321: cpuacct_charge <-update_curr <...>-1720 [002] dN.3 306.430322: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 <...>-1720 [002] d..2 306.430355: cpuacct_charge <-update_curr <...>-1720 [002] d..3 306.430357: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 bash-1652 [006] d.h2 306.430799: cpuacct_charge <-update_curr bash-1652 [006] d.h3 306.430802: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0xffffaf34012abdd8 <...>-199 [005] d.h2 306.430806: cpuacct_charge <-update_curr <...>-199 [005] d.h3 306.430809: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0xffffaf3400347c38 <...>-16 [001] d..2 306.430873: cpuacct_charge <-update_curr <...>-16 [001] d..3 306.430875: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 <...>-199 [005] d..2 306.430936: cpuacct_charge <-update_curr <...>-199 [005] d..3 306.430937: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 bash-1652 [006] d..2 306.430944: cpuacct_charge <-update_curr bash-1652 [006] d..3 306.430946: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 sshd-1649 [000] d..2 306.430990: cpuacct_charge <-update_curr sshd-1649 [000] d..3 306.430992: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.432844: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.432846: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.436848: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.436850: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.440868: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.440871: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.444867: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.444870: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 kworker/2:1-127 [002] d..2 306.446925: cpuacct_charge <-update_curr kworker/2:1-127 [002] d..3 306.446928: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.448868: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.448870: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0 rcu_preempt-10 [006] d..2 306.452869: cpuacct_charge <-update_curr rcu_preempt-10 [006] d..3 306.452872: cpuacct: (cpuacct_charge+0x36/0x1f0) regs=0x0
The only times regs has content is from the the interrupt handler (seen as the 'h' in the status portion of the trace.
-- Steve
| |