Re: [PATCH v6 1/3] perf: add PERF_RECORD_NAMESPACES to include namespaces related info

[Hari Bathini <hbathini@linux.vnet.ibm.com>]

Hi Eric,


On Thursday 16 February 2017 04:55 PM, 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.
>
> Plus who knows how long the name of the next namespace is going to be.
>

Agreed. Will drop name field from the structure and use an indexing
table to get names in userspace..

Thanks
Hari