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To: Stephen Hemminger <stephen@networkplumber.org>
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From: Remy Horton <remy.horton@intel.com>
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Date: Fri, 28 Oct 2016 15:48:09 +0800
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Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [RFC PATCH v2 2/3] lib: add bitrate statistics
	library
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On 28/10/2016 09:12, Stephen Hemminger wrote:
> On Fri, 28 Oct 2016 09:04:30 +0800
> Remy Horton <remy.horton@intel.com> wrote:
>
>> +
>> +struct rte_stats_bitrate_s {
>> +	uint64_t last_ibytes;
>> +	uint64_t last_obytes;
>> +	uint64_t peak_ibits;
>> +	uint64_t peak_obits;
>> +	uint64_t ewma_ibits;
>> +	uint64_t ewma_obits;
>> +};
>> +
>
> Reader/write access of 64 bit values is not safe on 32 bit platforms.
> I think you need to add a generation counter (see Linux kernel syncp)
> to handle 32 bit architecture. If done correctly, it would be a nop
> on 64 bit platforms.

I don't see a problem since this is private persistent data that is only 
read/written from rte_stats_bitrate_calc(), and once calculated it 
pushes them into the metrics library using rte_metrics_update_metrics(). 
The idea is that downstream consumers get the values using 
rte_metrics_get_values() rather than reading rte_stats_bitrate_s directly.

Having said that, what you mention quite likley affects the metrics 
library itself.. :)