linux-kernel - Re: [PATCH v2 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info

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Message-Id: <3d42dd8c-446d-f0de-1853-b78190a109c6@linux.vnet.ibm.com>
Date:   Fri, 9 Dec 2016 00:10:20 +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 v2 1/3] perf: add PERF_RECORD_NAMESPACES to include
 namespaces related info

Hi Peter,


Sorry for taking so long to respond...


On Thursday 24 November 2016 08:40 PM, Peter Zijlstra wrote:
> On Thu, Nov 24, 2016 at 08:14:29PM +0530, Hari Bathini wrote:
>> @@ -862,6 +875,19 @@ enum perf_event_type {
>>   	 */
>>   	PERF_RECORD_SWITCH_CPU_WIDE		= 15,
>>   
>> +	/*
>> +	 * struct {
>> +	 *	struct perf_event_header	header;
>> +	 *
>> +	 *	u32				pid, tid;
>> +	 *	u64				time;
> pid,tid and time are already present in sample_id. Many of the 'legacy'
> record have redundant information since we added sample_id, but most of
> the new ones haven't and rely on sample_all being set.

I tried using pid/tid from sample data, but realized that pid/tid in 
event_id
could be different from the one in sample data, at least for fork/namespaces
events, since __perf_event_header__init_id( ) that updates the sample data
is getting the pid/tid of current task.

I am not sure if it is advisable to change __perf_event_header__init_id( 
) for this..?

Thanks
Hari