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Date:   Tue, 22 May 2018 15:53:49 +0200
From:   Juri Lelli <juri.lelli@redhat.com>
To:     Waiman Long <longman@redhat.com>
Cc:     Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        kernel-team@fb.com, pjt@google.com, luto@amacapital.net,
        Mike Galbraith <efault@gmx.de>, torvalds@linux-foundation.org,
        Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH v8 6/6] cpuset: Allow reporting of sched domain
 generation info
Message-ID: <20180522135349.GB31040@localhost.localdomain>
References: <1526590545-3350-1-git-send-email-longman@redhat.com>
 <1526590545-3350-7-git-send-email-longman@redhat.com>
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Hi,

On 17/05/18 16:55, Waiman Long wrote:
> This patch enables us to report sched domain generation information.
> 
> If DYNAMIC_DEBUG is enabled, issuing the following command
> 
>   echo "file cpuset.c +p" > /sys/kernel/debug/dynamic_debug/control
> 
> and setting loglevel to 8 will allow the kernel to show what scheduling
> domain changes are being made.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>  kernel/cgroup/cpuset.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index fb8aa82b..8f586e8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -820,6 +820,12 @@ static int generate_sched_domains(cpumask_var_t **domains,
>  	}
>  	BUG_ON(nslot != ndoms);
>  
> +#ifdef CONFIG_DEBUG_KERNEL
> +	for (i = 0; i < ndoms; i++)
> +		pr_debug("generate_sched_domains dom %d: %*pbl\n", i,
> +			 cpumask_pr_args(doms[i]));
> +#endif
> +

While I'm always in favor of adding debug output, in this case I'm not
sure it's adding much to what we already print when booting with
sched_debug kernel command-line param, e.g.

--->8---
 Kernel command line: BOOT_IMAGE=/vmlinuz-4.17.0-rc5+ ... sched_debug

[...]

 smp: Bringing up secondary CPUs ...
 x86: Booting SMP configuration:
 .... node  #0, CPUs:        #1  #2  #3  #4  #5
 .... node  #1, CPUs:    #6  #7  #8  #9 #10 #11
 smp: Brought up 2 nodes, 12 CPUs
 smpboot: Max logical packages: 2
 smpboot: Total of 12 processors activated (45636.50 BogoMIPS)
 CPU0 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 0:{ span=0 cap=1016 }, 1:{ span=1 cap=1011 }, 2:{ span=2 }, 3:{ span=3 cap=1023 }, 4:{ span=4 }, 5:{ span=5 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU1 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 1:{ span=1 cap=1011 }, 2:{ span=2 }, 3:{ span=3 cap=1023 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 cap=1016 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU2 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 2:{ span=2 }, 3:{ span=3 cap=1023 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 cap=1016 }, 1:{ span=1 cap=1011 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU3 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 3:{ span=3 cap=1023 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 cap=1016 }, 1:{ span=1 cap=1011 }, 2:{ span=2 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU4 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 cap=1016 }, 1:{ span=1 cap=1011 }, 2:{ span=2 }, 3:{ span=3 cap=1023 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU5 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 5:{ span=5 }, 0:{ span=0 cap=1016 }, 1:{ span=1 cap=1011 }, 2:{ span=2 }, 3:{ span=3 cap=1023 }, 4:{ span=4 }
   domain-1: span=0-11 level=NUMA
    groups: 0:{ span=0-5 cap=6122 }, 6:{ span=6-11 cap=6141 }
 CPU6 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 cap=1021 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 CPU7 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 7:{ span=7 }, 8:{ span=8 cap=1021 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 CPU8 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 8:{ span=8 cap=1021 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 CPU9 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 cap=1021 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 CPU10 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 cap=1021 }, 9:{ span=9 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 CPU11 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 cap=1021 }, 9:{ span=9 }, 10:{ span=10 }
   domain-1: span=0-11 level=NUMA
    groups: 6:{ span=6-11 cap=6141 }, 0:{ span=0-5 cap=6122 }
 span: 0-11 (max cpu_capacity = 1024)

[...]

 generate_sched_domains dom 0: 6-11 <-- this and the one below is what
 generate_sched_domains dom 1: 0-5      you are adding
 CPU0 attaching NULL sched-domain.
 CPU1 attaching NULL sched-domain.
 CPU2 attaching NULL sched-domain.
 CPU3 attaching NULL sched-domain.
 CPU4 attaching NULL sched-domain.
 CPU5 attaching NULL sched-domain.
 CPU6 attaching NULL sched-domain.
 CPU7 attaching NULL sched-domain.
 CPU8 attaching NULL sched-domain.
 CPU9 attaching NULL sched-domain.
 CPU10 attaching NULL sched-domain.
 CPU11 attaching NULL sched-domain.
 CPU6 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }
 CPU7 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 7:{ span=7 }, 8:{ span=8 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }
 CPU8 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 8:{ span=8 }, 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }
 CPU9 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 9:{ span=9 }, 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 }
 CPU10 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 10:{ span=10 }, 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 }, 9:{ span=9 }
 CPU11 attaching sched-domain(s):
  domain-0: span=6-11 level=MC
   groups: 11:{ span=11 }, 6:{ span=6 }, 7:{ span=7 }, 8:{ span=8 }, 9:{ span=9 }, 10:{ span=10 }
 span: 6-11 (max cpu_capacity = 1024)
 CPU0 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 0:{ span=0 }, 1:{ span=1 }, 2:{ span=2 }, 3:{ span=3 }, 4:{ span=4 }, 5:{ span=5 }
 CPU1 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 1:{ span=1 }, 2:{ span=2 }, 3:{ span=3 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 }
 CPU2 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 2:{ span=2 }, 3:{ span=3 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 }, 1:{ span=1 }
 CPU3 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 3:{ span=3 }, 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 }, 1:{ span=1 }, 2:{ span=2 }
 CPU4 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 4:{ span=4 }, 5:{ span=5 }, 0:{ span=0 }, 1:{ span=1 }, 2:{ span=2 }, 3:{ span=3 }
 CPU5 attaching sched-domain(s):
  domain-0: span=0-5 level=MC
   groups: 5:{ span=5 }, 0:{ span=0 }, 1:{ span=1 }, 2:{ span=2 }, 3:{ span=3 }, 4:{ span=4 }
 span: 0-5 (max cpu_capacity = 1024)
 --->8---

 Do you think there is still a benefit in printing out what
 generate_sched_domains does?

 Best,

 - Juri