linux-kernel - Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info

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Date:   Fri, 16 Dec 2016 23:51:20 +0530
From:   Hari Bathini <hbathini@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     ast@...com, lkml <linux-kernel@...r.kernel.org>, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, mingo@...hat.com,
        daniel@...earbox.net, rostedt@...dmis.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        ebiederm@...ssion.com, sargun@...gun.me,
        Aravinda Prasad <aravinda@...ux.vnet.ibm.com>,
        brendan.d.gregg@...il.com
Subject: Re: [PATCH v4 1/3] perf: add PERF_RECORD_NAMESPACES to include
 namespaces related info

Hi Peter,


On Friday 16 December 2016 01:27 PM, Peter Zijlstra wrote:
> On Fri, Dec 16, 2016 at 11:57:47AM +0530, Hari Bathini wrote:
>>
>> On Friday 16 December 2016 12:16 AM, Peter Zijlstra wrote:
>>> On Fri, Dec 16, 2016 at 12:07:06AM +0530, Hari Bathini wrote:
>>>> +struct perf_ns_link_info {
>>>> +	__u64	dev;
>>>> +	__u64	ino;
>>>> +};
>>>> +
>>>> +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 +880,17 @@ enum perf_event_type {
>>>>   	 */
>>>>   	PERF_RECORD_SWITCH_CPU_WIDE		= 15,
>>>> +	/*
>>>> +	 * struct {
>>>> +	 *	struct perf_event_header	header;
>>>> +	 *	u32				pid;
>>>> +	 *	u32				tid;
>>>> +	 *	struct namespace_link_info	link_info[NAMESPACES_MAX];
>>>> +	 *	struct sample_id		sample_id;
>>>> +	 * };
>>>> +	 */
>>>> +	PERF_RECORD_NAMESPACES			= 16,
>>>> +
>>>>   	PERF_RECORD_MAX,			/* non-ABI */
>>>>   };
>>> What happens if a future kernel adds another namespace?
>>>
>> No impact unless NAMESPACES_MAX in include/uapi/linux/perf_event.h is
>> updated to accommodate that..
>> And if it is updated, the corresponding change is expected in perf-tool as
>> well..
> And what happens if you try and process old data files with the new
> tools or the other way around?

It works fine either way. I tested that..

> You must not expect lock-step updates for this to work.
>

Not required unless the tool is expected to process the new namespace data..

Thanks
Hari