From: Andrew Rybchenko <arybchenko@solarflare.com>
To: Bruce Richardson <bruce.richardson@intel.com>,
Ferruh Yigit <ferruh.yigit@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 18:00:34 +0300 [thread overview]
Message-ID: <bbdb646c-47cc-56fc-0e00-be577e01a86f@solarflare.com> (raw)
In-Reply-To: <20190716142823.GA1313@bricha3-MOBL.ger.corp.intel.com>
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.
next prev parent reply other threads:[~2019-07-16 15:01 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 [this message]
2019-07-16 15:29 ` Ferruh Yigit
2019-07-23 11:16 ` David Marchand
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