Re: [PATCH v3 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info

[Hari Bathini <hbathini@linux.vnet.ibm.com>]

Hi Eric,


On Monday 12 December 2016 11:57 PM, Eric W. Biederman wrote:
> Hari Bathini <hbathini@linux.vnet.ibm.com> writes:
>
>> With the advert of container technologies like docker, that depend
>> on namespaces for isolation, there is a need for tracing support for
>> namespaces. This patch introduces new PERF_RECORD_NAMESPACES event
>> for tracing based on namespaces related info.
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index c66a485..2a48fc6 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -344,7 +344,8 @@ struct perf_event_attr {
>>   				use_clockid    :  1, /* use @clockid for time fields */
>>   				context_switch :  1, /* context switch data */
>>   				write_backward :  1, /* Write ring buffer from end to beginning */
>> -				__reserved_1   : 36;
>> +				namespaces     :  1, /* include namespaces data */
>> +				__reserved_1   : 35;
>>   
>>   	union {
>>   		__u32		wakeup_events;	  /* wakeup every n events */
>> @@ -610,6 +611,18 @@ struct perf_event_header {
>>   	__u16	size;
>>   };
>>   
>> +enum {
>> +	NET_NS_INDEX		= 0,
>> +	UTS_NS_INDEX		= 1,
>> +	IPC_NS_INDEX		= 2,
>> +	PID_NS_INDEX		= 3,
>> +	USER_NS_INDEX		= 4,
>> +	MNT_NS_INDEX		= 5,
>> +	CGROUP_NS_INDEX		= 6,
>> +
>> +	NAMESPACES_MAX,		/* maximum available namespaces */
>> +};
>> +
>>   enum perf_event_type {
>>   
>>   	/*
>> @@ -862,6 +875,18 @@ enum perf_event_type {
>>   	 */
>>   	PERF_RECORD_SWITCH_CPU_WIDE		= 15,
>>   
>> +	/*
>> +	 * struct {
>> +	 *	struct perf_event_header	header;
>> +	 *
>> +	 *	u32				pid, tid;
>> +	 *	u64				dev_num;
>> +	 *	u64				inode_num[NAMESPACES_MAX];
> There needs to be one device number per inode.  While it is true that
> today the device number is always the same.  That is not necessarily so.
> I reserve the right to have the device number vary per namespace
> so that I don't need to implement a namespace of namespaces.
>
> These are st_dev and st_ino of the inode for the namespace.

Do you mean..

     st_dev = encode_dev(inode->i_sb->s_dev); ?
     st_ino = inode->i_ino; ?

Thanks
Hari