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

[Hari Bathini]

Hi Eric,


On Monday 12 December 2016 11:57 PM, Eric W. Biederman wrote:
> Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx> 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