Re: [Crash-utility] [PATCH] runq: make tasks in throttled cfs_rqs/rt_rqs displayed
----- Original Message -----
> Secondly, another question I have is the meaning of the
command's output.
>
> First, consider this "runq" output:
>
> crash> runq
> CPU 0 RUNQUEUE: ffff8800090436c0
> CURRENT: PID: 588 TASK: ffff88007e4877a0 COMMAND: "udevd"
> RT PRIO_ARRAY: ffff8800090437c8
> [no tasks queued]
> CFS RB_ROOT: ffff880009043740
> [118] PID: 2110 TASK: ffff88007d470860 COMMAND: "check-cdrom.sh"
> [118] PID: 2109 TASK: ffff88007f1247a0 COMMAND: "check-cdrom.sh"
> [118] PID: 2114 TASK: ffff88007f20e080 COMMAND: "udevd"
>
> CPU 1 RUNQUEUE: ffff88000905b6c0
> CURRENT: PID: 2113 TASK: ffff88007e8ac140 COMMAND: "udevd"
> RT PRIO_ARRAY: ffff88000905b7c8
> [no tasks queued]
> CFS RB_ROOT: ffff88000905b740
> [118] PID: 2092 TASK: ffff88007d7a4760 COMMAND: "MAKEDEV"
> [118] PID: 1983 TASK: ffff88007e59f140 COMMAND: "udevd"
> [118] PID: 2064 TASK: ffff88007e40f7a0 COMMAND: "udevd"
> [115] PID: 2111 TASK: ffff88007e4278a0 COMMAND: "kthreadd"
> crash>
>
> In the above case, the per-cpu "rq" structure addresses are shown as:
>
> CPU 0 RUNQUEUE: ffff8800090436c0
> CPU 1 RUNQUEUE: ffff88000905b6c0
>
> And embedded in each of the rq structures above are these two rb_root
> structures:
>
> CFS RB_ROOT: ffff880009043740 (embedded in rq @ffff8800090436c0)
> CFS RB_ROOT: ffff88000905b740 (embedded in rq @ffff88000905b6c0)
>
> And starting at those rb_root structures, the tree of tasks are
> dumped.
>
> Now, your "runq -q" option doesn't show any "starting point"
structure
> address, but rather they just show "CPU 0" and "CPU 1":
>
> crash> runq -g
> CPU 0
> CURRENT: PID: 588 TASK: ffff88007e4877a0 COMMAND: "udevd"
> RT PRIO_ARRAY: ffff8800090437c8
> [no tasks queued]
> CFS RB_ROOT: ffff880009093548
> [118] PID: 2110 TASK: ffff88007d470860 COMMAND: "check-cdrom.sh"
> [118] PID: 2109 TASK: ffff88007f1247a0 COMMAND: "check-cdrom.sh"
> [118] PID: 2114 TASK: ffff88007f20e080 COMMAND: "udevd"
>
> CPU 1
> CURRENT: PID: 2113 TASK: ffff88007e8ac140 COMMAND: "udevd"
> RT PRIO_ARRAY: ffff88000905b7c8
> [no tasks queued]
> CFS RB_ROOT: ffff880009093548
> [118] PID: 2092 TASK: ffff88007d7a4760 COMMAND: "MAKEDEV"
> [118] PID: 1983 TASK: ffff88007e59f140 COMMAND: "udevd"
> [118] PID: 2064 TASK: ffff88007e40f7a0 COMMAND: "udevd"
> [115] PID: 2111 TASK: ffff88007e4278a0 COMMAND: "kthreadd"
> crash>
>
> I would think that there might be a useful address of a per-cpu
> structure that could be shown there as well?
OK, this is added.
OK, but now your addition just mimics the "runq" output. You are just
calculating the CFS "runq" address for display, but that address does
not passed to (or used by) either dump_tasks_in_task_group_rt_rq()
or dump_tasks_in_task_group_cfs_rq().
I was suggesting that you display per-cpu addresses generated from the
init_task_group/root_task_group task_group structures. Wouldn't it make
more sense for it to show both the per-cpu "rt_rq" and "cfs_rq"
addresses?
In other words, maybe something like:
CPU 0 TASK_GROUP RT_RQ: ffff88021e213e28 TASK_GROUP CFS_RQ: ffff88021e213d30
CURRENT: ...
Aside from that, the latest patch passes my tests OK.
Thanks,
Dave