Re: [PATCH 5 of 6 v2] xen: tracing: introduce per-scheduler trace event IDs

[George Dunlap <george.dunlap@eu.citrix.com>]

On 12/12/12 02:52, Dario Faggioli wrote:
> So that it becomes possible to create scheduler specific trace records,
> within each scheduler, without worrying about the overlapping, and also
> without giving up being able to recognise them univocally. The latter
> is deemed as useful, since we can have more than one scheduler running
> at the same time, thanks to cpupools.
>
> The event ID is 12 bits, and this change uses the upper 3 of them for
> the 'scheduler ID'. This means we're limited to 8 schedulers and to
> 512 scheduler specific tracing events. Both seem reasonable limitations
> as of now.
>
> This also converts the existing credit2 tracing (the only scheduler
> generating tracing events up to now) to the new system.
>
> Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>

Acked-by: George Dunlap <george.dunlap@eu.citrix.com>

> ---
> Changes from v1:
>   * The event ID generaion macro is now called `TRC_SCHED_CLASS_EVT()',
>     and has been generalized and put in trace.h, as suggested.
>   * The handling of per-scheduler tracing IDs and masks have been
>     restructured, properly naming "ID" the numerical identifiers
>     and "MASK" the bitmasks, as requested.
>
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -29,18 +29,22 @@
>   #define d2printk(x...)
>   //#define d2printk printk
>   
> -#define TRC_CSCHED2_TICK        TRC_SCHED_CLASS + 1
> -#define TRC_CSCHED2_RUNQ_POS    TRC_SCHED_CLASS + 2
> -#define TRC_CSCHED2_CREDIT_BURN TRC_SCHED_CLASS + 3
> -#define TRC_CSCHED2_CREDIT_ADD  TRC_SCHED_CLASS + 4
> -#define TRC_CSCHED2_TICKLE_CHECK TRC_SCHED_CLASS + 5
> -#define TRC_CSCHED2_TICKLE       TRC_SCHED_CLASS + 6
> -#define TRC_CSCHED2_CREDIT_RESET TRC_SCHED_CLASS + 7
> -#define TRC_CSCHED2_SCHED_TASKLET TRC_SCHED_CLASS + 8
> -#define TRC_CSCHED2_UPDATE_LOAD   TRC_SCHED_CLASS + 9
> -#define TRC_CSCHED2_RUNQ_ASSIGN   TRC_SCHED_CLASS + 10
> -#define TRC_CSCHED2_UPDATE_VCPU_LOAD   TRC_SCHED_CLASS + 11
> -#define TRC_CSCHED2_UPDATE_RUNQ_LOAD   TRC_SCHED_CLASS + 12
> +/*
> + * Credit2 tracing events ("only" 512 available!). Check
> + * include/public/trace.h for more details.
> + */
> +#define TRC_CSCHED2_TICK             TRC_SCHED_CLASS_EVT(CSCHED2, 1)
> +#define TRC_CSCHED2_RUNQ_POS         TRC_SCHED_CLASS_EVT(CSCHED2, 2)
> +#define TRC_CSCHED2_CREDIT_BURN      TRC_SCHED_CLASS_EVT(CSCHED2, 3)
> +#define TRC_CSCHED2_CREDIT_ADD       TRC_SCHED_CLASS_EVT(CSCHED2, 4)
> +#define TRC_CSCHED2_TICKLE_CHECK     TRC_SCHED_CLASS_EVT(CSCHED2, 5)
> +#define TRC_CSCHED2_TICKLE           TRC_SCHED_CLASS_EVT(CSCHED2, 6)
> +#define TRC_CSCHED2_CREDIT_RESET     TRC_SCHED_CLASS_EVT(CSCHED2, 7)
> +#define TRC_CSCHED2_SCHED_TASKLET    TRC_SCHED_CLASS_EVT(CSCHED2, 8)
> +#define TRC_CSCHED2_UPDATE_LOAD      TRC_SCHED_CLASS_EVT(CSCHED2, 9)
> +#define TRC_CSCHED2_RUNQ_ASSIGN      TRC_SCHED_CLASS_EVT(CSCHED2, 10)
> +#define TRC_CSCHED2_UPDATE_VCPU_LOAD TRC_SCHED_CLASS_EVT(CSCHED2, 11)
> +#define TRC_CSCHED2_UPDATE_RUNQ_LOAD TRC_SCHED_CLASS_EVT(CSCHED2, 12)
>   
>   /*
>    * WARNING: This is still in an experimental phase.  Status and work can be found at the
> diff --git a/xen/include/public/trace.h b/xen/include/public/trace.h
> --- a/xen/include/public/trace.h
> +++ b/xen/include/public/trace.h
> @@ -57,6 +57,32 @@
>   #define TRC_SCHED_CLASS     0x00022000   /* Scheduler-specific    */
>   #define TRC_SCHED_VERBOSE   0x00028000   /* More inclusive scheduling */
>   
> +/*
> + * The highest 3 bits of the last 12 bits of TRC_SCHED_CLASS above are
> + * reserved for encoding what scheduler produced the information. The
> + * actual event is encoded in the last 9 bits.
> + *
> + * This means we have 8 scheduling IDs available (which means at most 8
> + * schedulers generating events) and, in each scheduler, up to 512
> + * different events.
> + */
> +#define TRC_SCHED_ID_BITS 3
> +#define TRC_SCHED_ID_SHIFT (TRC_SUBCLS_SHIFT - TRC_SCHED_ID_BITS)
> +#define TRC_SCHED_ID_MASK (((1UL<<TRC_SCHED_ID_BITS) - 1) << TRC_SCHED_ID_SHIFT)
> +#define TRC_SCHED_EVT_MASK (~(TRC_SCHED_ID_MASK))
> +
> +/* Per-scheduler IDs, to identify scheduler specific events */
> +#define TRC_SCHED_CSCHED   0
> +#define TRC_SCHED_CSCHED2  1
> +#define TRC_SCHED_SEDF     2
> +#define TRC_SCHED_ARINC653 3
> +
> +/* Per-scheduler tracing */
> +#define TRC_SCHED_CLASS_EVT(_c, _e) \
> +  ( ( TRC_SCHED_CLASS | \
> +      ((TRC_SCHED_##_c << TRC_SCHED_ID_SHIFT) & TRC_SCHED_ID_MASK) ) + \
> +    (_e & TRC_SCHED_EVT_MASK) )
> +
>   /* Trace classes for Hardware */
>   #define TRC_HW_PM           0x00801000   /* Power management traces */
>   #define TRC_HW_IRQ          0x00802000   /* Traces relating to the handling of IRQs */