linux-kernel - Re: [PATCH 1/2] perf: add container identifier entry in perf sample data

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Date:   Fri, 26 Aug 2016 09:35:02 +0530
From:   Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
To:     Hari Bathini <hbathini@...ux.vnet.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, ast@...com,
        lkml <linux-kernel@...r.kernel.org>, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, mingo@...hat.com,
        sargun@...gun.me, Aravinda Prasad <aravinda@...ux.vnet.ibm.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        daniel@...earbox.net
Subject: Re: [PATCH 1/2] perf: add container identifier entry in perf sample
 data

On Thu, Aug 25, 2016 at 10:50:18PM +0530, Hari Bathini wrote:
> 
> 
> On Thursday 25 August 2016 06:31 PM, Peter Zijlstra wrote:
> >On Thu, Aug 25, 2016 at 05:27:54PM +0530, Hari Bathini wrote:
> >
> >>diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> >>index c66a485..fb4f902 100644
> >>--- a/include/uapi/linux/perf_event.h
> >>+++ b/include/uapi/linux/perf_event.h
> >>@@ -139,8 +139,9 @@ enum perf_event_sample_format {
> >>  	PERF_SAMPLE_IDENTIFIER			= 1U << 16,
> >>  	PERF_SAMPLE_TRANSACTION			= 1U << 17,
> >>  	PERF_SAMPLE_REGS_INTR			= 1U << 18,
> >>+	PERF_SAMPLE_CID				= 1U << 19,
> >>-	PERF_SAMPLE_MAX = 1U << 19,		/* non-ABI */
> >>+	PERF_SAMPLE_MAX = 1U << 20,		/* non-ABI */
> >>  };
> >This forgets to update the comment that goes with PERF_RECORD_SAMPLE.
> >This patch would also need an update to the manpage:
> >
> >   http://git.kernel.org/cgit/docs/man-pages/man-pages.git/tree/man2/perf_event_open.2
> >
> >   http://www.man7.org/linux/man-pages/man2/perf_event_open.2.html
> >
> >>+	if (sample_type & PERF_SAMPLE_CID) {
> >>+		int size = sizeof(u64);
> >>+
> >>+		/*
> >>+		 * Container identifier for a given task.
> >>+		 * Using cgroup namespace inode number for this.
> >>+		 */
> >>+		data->cid_entry.cid = current->nsproxy->cgroup_ns->ns.inum;
> >>+		data->cid_entry.reserved = 0;
> >>+		header->size += size;
> >>+	}
> >>  }
> >Does this compile with CONFIG_CGROUP=n ?
> >
> 
> My bad. Will update..
> Actually, on second thought, how about using inode number of some
> other namespace that any container would have (mount, probably?)..

I am not sure about every implementation of 'containers' but I would
think that the cgroup namespace is the right choice here. Mount
namespaces can be potentially shared between containers AFAIK.

Ananth