[dpdk-dev] [PATCH] docs: add statistics read frequency to fm10k guide
> -Original Message- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Thomas Monjalon > Sent: Monday, February 8, 2016 4:01 PM > To: Van Haaren, Harry > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH] docs: add statistics read frequency to > fm10k guide > > 2016-02-08 15:42, Harry van Haaren: > > This patch documents that the statistics of fm10k based NICs must be > > read regularly in order to avoid an undetected 32 bit integer-overflow. > > > > Signed-off-by: Harry van Haaren > > --- > > doc/guides/nics/fm10k.rst| 16 > > doc/guides/rel_notes/release_2_3.rst | 4 > > Thanks for improving the doc. > I think we should not add it to the release notes. Other opinions? In general it shouldn't be required to add a note about doc changes to the release note. In this case the note part may make more sense in the "Known Issues" section of the release note. John. --
[dpdk-dev] [PATCH] docs: add statistics read frequency to fm10k guide
2016-02-08 15:42, Harry van Haaren: > This patch documents that the statistics of fm10k based NICs must be > read regularly in order to avoid an undetected 32 bit integer-overflow. > > Signed-off-by: Harry van Haaren > --- > doc/guides/nics/fm10k.rst| 16 > doc/guides/rel_notes/release_2_3.rst | 4 Thanks for improving the doc. I think we should not add it to the release notes. Other opinions?
[dpdk-dev] [PATCH] docs: add statistics read frequency to fm10k guide
> From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com] > 2016-02-08 15:42, Harry van Haaren: > > This patch documents that the statistics of fm10k based NICs must be > > read regularly in order to avoid an undetected 32 bit integer-overflow. > > > > Signed-off-by: Harry van Haaren > > --- > > doc/guides/nics/fm10k.rst| 16 > > doc/guides/rel_notes/release_2_3.rst | 4 > > Thanks for improving the doc. > I think we should not add it to the release notes. Other opinions? I was unsure on including it, and have no problem with it not being included. V2?
[dpdk-dev] [PATCH] docs: add statistics read frequency to fm10k guide
This patch documents that the statistics of fm10k based NICs must be read regularly in order to avoid an undetected 32 bit integer-overflow. Signed-off-by: Harry van Haaren --- doc/guides/nics/fm10k.rst| 16 doc/guides/rel_notes/release_2_3.rst | 4 2 files changed, 20 insertions(+) diff --git a/doc/guides/nics/fm10k.rst b/doc/guides/nics/fm10k.rst index 4206b7f..4250c9e 100644 --- a/doc/guides/nics/fm10k.rst +++ b/doc/guides/nics/fm10k.rst @@ -65,3 +65,19 @@ The FM1 family of NICS support a maximum of a 15K jumbo frame. The value is fixed and cannot be changed. So, even when the ``rxmode.max_rx_pkt_len`` member of ``struct rte_eth_conf`` is set to a value lower than 15364, frames up to 15364 bytes can still reach the host interface. + +Statistic Polling Frequency +~~~ + +The FM1 NICs expose a set of statistics via the PCI BARs. These statistics +are read from the hardware registers when ``rte_eth_stats_get()`` or +``rte_eth_xstats_get()`` is called. The packet counting registers are 32 bits +while the byte counting registers are 48 bits. As a result, the statistics must +be polled regularly in order to ensure the consistency of the returned reads. + +Given the PCIe Gen3 x8, about 50Gbps of traffic can occur. With 64 byte packets +this gives almost 100 million packets/second, causing 32 bit integer overflow +after approx 40 seconds. To ensure these overflows are detected and accounted +for in the statistics, it is necessary to read statistic regularly. It is +suggested to read stats every 20 seconds, which will gaurantee the statistics +are accurate. diff --git a/doc/guides/rel_notes/release_2_3.rst b/doc/guides/rel_notes/release_2_3.rst index 99de186..f966940 100644 --- a/doc/guides/rel_notes/release_2_3.rst +++ b/doc/guides/rel_notes/release_2_3.rst @@ -15,6 +15,10 @@ EAL Drivers ~~~ +* **FM10K: Statistics Polling Frequency** + + A section has been added to the NIC guide for fm10k about the time + between reading statistics and 32 bit packet counter overflows. Libraries ~ -- 2.5.0