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

[kajoljain <kjain@linux.ibm.com>]

On 12/21/20 11:10 AM, Michael Ellerman wrote:
> 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?

Hi Michael,
      We don't have any such document which says any event with "FREE_"
in the name will be invalid. So I will replace strstr check with strcmp
to look for events with names have "FREE" or "CPM_FREE" at start.

Thanks,
Kajol Jain

> 
> cheers
>