Re: [Xen-devel] [PATCH] xen: sched: improve debug dump output.

[Meng Xu <mengxu@xxxxxxxxxxxxx>]

Hi Dario,

I'm commenting on the rtds part.

On Thu, Jan 26, 2017 at 11:52 AM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
> Scheduling information debug dump for Credit2 is hard
> to read as it contains the same information repeated
> multiple time in different ways.
>
> In fact, in Credit2, CPUs are grouped in runqueus.
> Here's the current debug output:
>
>  CPU[00]  sibling=00000000,00000003, core=00000000,000000ff
>     run: [32767.0] flags=0 cpu=0 credit=-1073741824 [w=0] load=0 (~0%)
>       1: [0.3] flags=0 cpu=2 credit=3273410 [w=256] load=262144 (~100%)
>       2: [0.4] flags=0 cpu=2 credit=2974954 [w=256] load=262144 (~100%)
>  CPU[01]  sibling=00000000,00000003, core=00000000,000000ff
>     run: [32767.1] flags=0 cpu=1 credit=-1073741824 [w=0] load=0 (~0%)
>       1: [0.3] flags=0 cpu=2 credit=3273410 [w=256] load=262144 (~100%)
>       2: [0.4] flags=0 cpu=2 credit=2974954 [w=256] load=262144 (~100%)
>  CPU[02]  sibling=00000000,0000000c, core=00000000,000000ff
>     run: [0.2] flags=2 cpu=2 credit=3556909 [w=256] load=262144 (~100%)
>       1: [0.3] flags=0 cpu=2 credit=3273410 [w=256] load=262144 (~100%)
>       2: [0.4] flags=0 cpu=2 credit=2974954 [w=256] load=262144 (~100%)
>
> Here, CPUs 0, 1 and 2, are all part of runqueue 0,
> the content of which (which, BTW, is d0v3 and d0v4)
> is printed 3 times! It is also not very useful to
> see the details of the idle vcpus, as they're always
> the same (except for the vCPU ids).
>
> With this change, we print:
>  - pCPUs details and, for non idle ones, what vCPU
>    they're running;
>  - the runqueue content, once and for all.
>
>  Runqueue 0:
>  CPU[00] runq=0, sibling=00000000,00000003, core=00000000,000000ff
>     run: [0.15] flags=2 cpu=0 credit=5804742 [w=256] load=3655 (~1%)
>  CPU[01] runq=0, sibling=00000000,00000003, core=00000000,000000ff
>  CPU[02] runq=0, sibling=00000000,0000000c, core=00000000,000000ff
>     run: [0.3] flags=2 cpu=2 credit=6674856 [w=256] load=262144 (~100%)
>  CPU[03] runq=0, sibling=00000000,0000000c, core=00000000,000000ff
>  RUNQ:

What is the difference between RUNQ and Runqueue 0 in the message?

>       0: [0.1] flags=0 cpu=2 credit=6561215 [w=256] load=262144 (~100%)
>       1: [0.2] flags=0 cpu=2 credit=5812356 [w=256] load=262144 (~100%)
>
> Stop printing details of idle vCPUs also in Credit1
> and RTDS (they're pretty useless in there too).
>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Cc: Anshul Makkar <anshul.makkar@xxxxxxxxxx>
> Cc: Meng Xu <mengxu@xxxxxxxxxxxxx>
> ---
>  xen/common/sched_credit.c  |    6 ++--
>  xen/common/sched_credit2.c |   72 
> +++++++++++++++++++++-----------------------
>  xen/common/sched_rt.c      |    9 +++++-
>  xen/common/schedule.c      |    7 ++--
>  4 files changed, 49 insertions(+), 45 deletions(-)
>

> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 24b4b22..f2d979c 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -320,10 +320,17 @@ static void
>  rt_dump_pcpu(const struct scheduler *ops, int cpu)
>  {
>      struct rt_private *prv = rt_priv(ops);
> +    struct rt_vcpu *svc;
>      unsigned long flags;
>
>      spin_lock_irqsave(&prv->lock, flags);
> -    rt_dump_vcpu(ops, rt_vcpu(curr_on_cpu(cpu)));
> +    printk("CPU[%02d]\n", cpu);

We probably do not need this printk().
In rt_dump_vcpu(), we will print out the CPU number.

> +    /* current VCPU (nothing to say if that's the idle vcpu). */
> +    svc = rt_vcpu(curr_on_cpu(cpu));
> +    if ( svc && !is_idle_vcpu(svc->vcpu) )
> +    {
> +        rt_dump_vcpu(ops, svc);
> +    }

Maybe it is better to print the CPU number if the CPU is running an idle VCPU.
The printk info could be:
         printk("CPU[%02d]: idle\n", cpu);

>      spin_unlock_irqrestore(&prv->lock, flags);
>  }

Thanks,

Meng

------------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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