From: ebiederm@xmission.com (Eric W. Biederman)
To: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: ast@fb.com, peterz@infradead.org, lkml <linux-kernel@vger.kernel.org>,
        acme@kernel.org, alexander.shishkin@linux.intel.com, mingo@redhat.com,
        daniel@iogearbox.net, rostedt@goodmis.org,
        Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
        sargun@sargun.me, Aravinda Prasad <aravinda@linux.vnet.ibm.com>,
        brendan.d.gregg@gmail.com
References: <148156671980.4651.13017595439842763683.stgit@hbathini.in.ibm.com>
        <148156676528.4651.9323274278676831770.stgit@hbathini.in.ibm.com>
Date: Tue, 13 Dec 2016 07:27:35 +1300
In-Reply-To: <148156676528.4651.9323274278676831770.stgit@hbathini.in.ibm.com>
        (Hari Bathini's message of "Mon, 12 Dec 2016 23:49:36 +0530")
Message-ID: <871sxdf1ew.fsf@xmission.com>
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Subject: Re: [PATCH v3 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info
Sender: linux-kernel-owner@vger.kernel.org
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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.

> +	 *	struct sample_id		sample_id;
> +	 * };
> +	 */
> +	PERF_RECORD_NAMESPACES			= 16,
> +
>  	PERF_RECORD_MAX,			/* non-ABI */
>  };