From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Andrew Rybchenko <arybchenko@solarflare.com>,
Bruce Richardson <bruce.richardson@intel.com>
Cc: "A.McLoughlin" <aideen.mcloughlin@intel.com>,
Wenzhuo Lu <wenzhuo.lu@intel.com>,
Jingjing Wu <jingjing.wu@intel.com>,
Bernard Iremonger <bernard.iremonger@intel.com>,
dev@dpdk.org, david.marchand@redhat.com, stable@dpdk.org,
Thomas Monjalon <thomas@monjalon.net>,
Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH] app/testpmd: fix doubling of 'total TX dropped'
Date: Tue, 16 Jul 2019 16:29:36 +0100 [thread overview]
Message-ID: <ef0d49bd-8885-1702-5481-40d3394eab46@intel.com> (raw)
In-Reply-To: <bbdb646c-47cc-56fc-0e00-be577e01a86f@solarflare.com>
On 7/16/2019 4:00 PM, Andrew Rybchenko wrote:
> On 7/16/19 5:28 PM, Bruce Richardson wrote:
>> On Tue, Jul 16, 2019 at 03:23:03PM +0100, Ferruh Yigit wrote:
>>> On 7/16/2019 1:23 PM, Andrew Rybchenko wrote:
>>>> On 7/15/19 5:53 PM, Ferruh Yigit wrote:
>>>>> On 7/12/2019 9:32 AM, A.McLoughlin wrote:
>>>>>> The 'Accumulated forward statistics for all ports' incorrectly displayed
>>>>>> double the actual value for 'total_tx_dropped'. This was because 2
>>>>>> lines in the same function both incremented total_tx_dropped every time
>>>>>> a packet was dropped. I removed one of these lines to fix this issue.
>>>>>>
>>>>>> Fixes: 53324971a14e ("app/testpmd: display/clear forwarding stats on demand")
>>>>>> Cc: david.marchand@redhat.com
>>>>>> Cc: stable@dpdk.org
>>>>>>
>>>>>> Signed-off-by: A.McLoughlin <aideen.mcloughlin@intel.com>
>>>>>> ---
>>>>>> app/test-pmd/testpmd.c | 1 -
>>>>>> 1 file changed, 1 deletion(-)
>>>>>>
>>>>>> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
>>>>>> index 3ed3523b7..c41bada50 100644
>>>>>> --- a/app/test-pmd/testpmd.c
>>>>>> +++ b/app/test-pmd/testpmd.c
>>>>>> @@ -1555,7 +1555,6 @@ fwd_stats_display(void)
>>>>>> total_recv += stats.ipackets;
>>>>>> total_xmit += stats.opackets;
>>>>>> total_rx_dropped += stats.imissed;
>>>>>> - total_tx_dropped += ports_stats[pt_id].tx_dropped;
>>>>>> total_tx_dropped += stats.oerrors;
>>>>>> total_rx_nombuf += stats.rx_nombuf;
>>>>>>
>>>>>>
>>>>>
>>>>> Hi Aideen,
>>>>>
>>>>> Indeed 'rte_eth_stats->oerrors' and 'tx_dropped' are different values,
>>>>>
>>>>> in testpmd, 'TX-total' is taken as "total_xmit + total_tx_dropped", from this
>>>>> description it may be fair to say
>>>>> "total_tx_dropped = oerrors + tx_dropped"
>>>>>
>>>>> This is easier to see in HW devices, 'oerrors' is the packets sent to HW but HW
>>>>> reported failure for some reason, so these packets not transmitted to the medium.
>>>>> 'tx_dropped' is mostly calculated by application, driver returns packets that
>>>>> can't able to sent to HW, so application can re-try to send or free them and
>>>>> increase 'tx_dropped' counter.
>>>>>
>>>>>
>>>>> The problem is in the virtual drivers, the packets not able to sent are
>>>>> calculated as 'oerrors' and tx_burst functions returns the number of the
>>>>> successfully sent packets which cause application calculate remaining ones as
>>>>> 'tx_dropped' which cause the duplication.
>>>>
>>>> I don't understand how it is. Tx burst returns a number of owned packets
>>>> (either successfully transmitted or internally dropped/freed). If it is
>>>> smaller than number of packets in request, other packets are either
>>>> retried or calculated as tx_dropped.
>>>
>>> Virtual PMDs, at least the ones I checked, calculating not sent packets as
>>> error, also application calculates them as tx_dropped.
>>>
>>> Like:
>>> https://git.dpdk.org/dpdk/tree/drivers/net/ring/rte_eth_ring.c?h=v19.08-rc1#n97
>>>
>> That is probably incorrect to do. Virtual PMDs should behave as real ones
>> do as far as possible. I think we should change them to not count as errors
>> any that are not handled by the driver, provided those are returned to the
>> app.
>
> I agree with Bruce. It is a bug in ring PMD. If so, too fast attempts to
> transmit packets will blow up err_pkts counter.
>
+1, as far as I can see following PMDs requires fixing:
ring
kni
pcap
tap
next prev parent reply other threads:[~2019-07-16 15:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 8:32 [dpdk-stable] " A.McLoughlin
2019-07-12 13:33 ` Iremonger, Bernard
2019-07-15 14:53 ` [dpdk-stable] [dpdk-dev] " Ferruh Yigit
2019-07-16 12:23 ` Andrew Rybchenko
2019-07-16 14:23 ` Ferruh Yigit
2019-07-16 14:28 ` Bruce Richardson
2019-07-16 15:00 ` Andrew Rybchenko
2019-07-16 15:29 ` Ferruh Yigit [this message]
2019-07-23 11:16 ` David Marchand
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