[Crash-utility] per_cpu__xxxxx

[Dave Anderson]

olivier.daudel at u-paris10.fr wrote:

> Hi Dave,
> In reading your reply arroud per_cpu__xxxxx, i have understood my mistake.
> For a new bee ... i think we could add someting like this in your help.
> =====================================================

Yep -- I've thought of adding a "per_cpu" command to be able to display
any per_cpu variable, but have never had the time to implement it.
But your tutorial below explains how it would have to be done.

Thanks,
  Dave

>
>
> Spetial mention arround per_cpu__xxxx (with Intel only ?) in SMP context.
>
> First step : you have to find __per_cpu_offset
> crash> __per_cpu_offset
> __per_cpu_offset = $1 =
> {25182048, 25214816, 25247584, 25280352, 25313120, 25345888, 25378656,
>   25411424, 25444192, 25476960, 25509728, 25542496, 25575264, 25608032,
>   25640800, 25673568, 25706336, 25739104, 25771872, 25804640, 25837408,
>   25870176, 25902944, 25935712, 25968480, 26001248, 26034016, 26066784,
>   26099552, 26132320, 26165088, 26197856}
>
> Second setp : use whatis, struct and sym with your per_cpu__xxxxx
> crash> whatis per_cpu__irq_stat
> irq_cpustat_t per_cpu__irq_stat;
> crash> irq_cpustat_t -o
> No struct type named irq_cpustat_t.
> struct {
>     [0] unsigned int __softirq_pending;
>     [4] long unsigned int idle_timestamp;
>     [8] unsigned int __nmi_count;
>    [12] unsigned int apic_timer_irqs;
> }
> SIZE: 128
> crash> sym per_cpu__irq_stat
> c0407380 (D) per_cpu__irq_stat
>
> Third step : use eval to determine the correct address
> crash> eval c0407380 + 25214816
> hexadecimal: c1c132e0
> [...]
>
> (one day, i shall try to do a small patch with options -h, -d, -o and
> -2 (-b better, but already used) to select the proper choice when we
> want to !!!)
>
> Last step : you may now access to the per_cpu__xxxxx of second CPU
> crash> rd -d c1c132e0 4
> c1c132e0:             0     16918620            0     17218691
>
> A nicer example, with a well defined structure :
>
> crash> sym per_cpu__kstat
> c0408be0 (D) per_cpu__kstat
> crash> whatis per_cpu__kstat
> struct kernel_stat per_cpu__kstat;
> crash> eval c0408be0 + 25214816
> hexadecimal: c1c14b40
> [...]
> crash> kernel_stat c1c14b40
> struct kernel_stat {
>   cpustat = {
>     user = 535936,
>     nice = 3864001,
>     system = 33693,
>     softirq = 289,
>     irq = 526,
>     idle = 12992235,
>     iowait = 23818,
>     steal = 0
>   },
>   irqs = {8702265, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 77403, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     4788, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     18433, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>     0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
> }
>
> ----------------------------------------------------------------
> Ce message a ete envoye par IMP, grace a l'Universite Paris 10 Nanterre
>
> ----- Fin du message transféré -----
>
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> Ce message a ete envoye par IMP, grace a l'Universite Paris 10 Nanterre
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