Re: [PATCH v2] powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

[Michael Ellerman <mpe@ellerman.id.au>]

Kajol Jain <kjain@linux.ibm.com> writes:
> hv_24x7 performance monitoring unit creates list of supported events
> from the event catalog obtained via HCALL. hv_24x7 catalog could also
> contain invalid or dummy events (with names like FREE_* or CPM_FREE_*
> and RESERVED*). These events do not have any hardware counters
> backing them. So patch adds a check to string compare the event names
> to filter out them.
>
> Result in power9 machine:
>
> Before this patch:
> .....
>   hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
>   hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
>   hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
>   hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
>   hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
>   hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
>   hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
>   hv_24x7/RESERVED_NEST1,chip=?/                     [Kernel PMU event]
>   hv_24x7/RESERVED_NEST10,chip=?/                    [Kernel PMU event]
>   hv_24x7/RESERVED_NEST11,chip=?/                    [Kernel PMU event]
>   hv_24x7/RESERVED_NEST12,chip=?/                    [Kernel PMU event]
>   hv_24x7/RESERVED_NEST13,chip=?/                    [Kernel PMU event]
> ......
>
> Dmesg:
> [    0.000362] printk: console [hvc0] enabled
> [    0.815452] hv-24x7: read 1530 catalog entries, created 537 event attrs
> (0 failures), 275 descs
>
> After this patch:
> ......
>   hv_24x7/PM_XLINK2_OUT_ODD_AVLBL_CYC,chip=?/        [Kernel PMU event]
>   hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
>   hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
>   hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
>   hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
>   hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
>   hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
>   hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
>   hv_24x7/TOD,chip=?/                                [Kernel PMU event]
> ......
>
> Demsg:
> [    0.000357] printk: console [hvc0] enabled
> [    0.808592] hv-24x7: read 1530 catalog entries, created 509 event attrs
> (0 failures), 275 descs
>
> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> ---
>  arch/powerpc/perf/hv-24x7.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> ---
> Changelog
> v1 -> v2
> - Include "RESERVED*" as part of the invalid event check as
>   suggested by Madhavan Srinivasan
> - Add new helper function "ignore_event" to check invalid/dummy
>   events as suggested by Michael Ellerman
> - Remove pr_info to print each invalid event as suggested by
>   Michael Ellerman
> ---
> diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
> index 6e7e820508df..1a6004d88f98 100644
> --- a/arch/powerpc/perf/hv-24x7.c
> +++ b/arch/powerpc/perf/hv-24x7.c
> @@ -764,6 +764,16 @@ static ssize_t catalog_event_len_validate(struct hv_24x7_event_data *event,
>  	return ev_len;
>  }
>  
> +/*
> + * Return true incase of invalid or dummy events with names like FREE_* or CPM_FREE_*
> + * and RESERVED*
> + */
> +static bool ignore_event(const char *name)
> +{
> +	return (strstr(name, "FREE_") || !strncmp(name, "RESERVED", 8)) ?
> +			true : false;

That's FREE_ anywhere in the string, which seems a bit loose.

Do we have any documentation or anything that tells us that any event
with "FREE_" in the name will always be invalid?

cheers