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Date: Thu, 16 Feb 2017 12:47:17 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>, ast@fb.com,
        lkml <linux-kernel@vger.kernel.org>, acme@kernel.org,
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        Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
        sargun@sargun.me, Aravinda Prasad <aravinda@linux.vnet.ibm.com>,
        brendan.d.gregg@gmail.com, jolsa@redhat.com
Subject: Re: [PATCH v6 1/3] perf: add PERF_RECORD_NAMESPACES to include
 namespaces related info
Message-ID: <20170216114717.GY6500@twins.programming.kicks-ass.net>
References: <148654265580.27983.8822211570127163843.stgit@hbathini.in.ibm.com>
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On Fri, Feb 17, 2017 at 12:25:27AM +1300, Eric W. Biederman wrote:
> > +/*
> > + * The maximum size of the name of each namespace
> > + */
> > +#define NS_NAME_SIZE				8
> > +
> > +struct perf_ns_link_info {
> > +	char	name[NS_NAME_SIZE];
> > +	__u64	dev;
> > +	__u64	ino;
> > +};
> 
> Ugh. I missed the name the first time around.
> 
> That really looks like useless clutter.  You already know the index so
> the name doesn't add any information, so unless I am missing something
> that name will just slow down the perf kernel implementation with
> useless work.
> 
> The userspace reader can have the information just as reliably by
> looking at the index and indexing into a table.
> 
> The set of namespaces changes slowly enough that this is not likely to
> be a problem in practice.  Especially as perf is released with the
> kernel.

Right; Hari, please ditch that name thing.