From: Vlad Zolotarov <vladz@cloudius-systems.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
Thomas Monjalon <thomas.monjalon@6wind.com>,
"Zhang, Helin" <helin.zhang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"Kirsher, Jeffrey T" <jeffrey.t.kirsher@intel.com>,
"Brandeburg, Jesse" <jesse.brandeburg@intel.com>
Subject: Re: [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598
Date: Tue, 27 Oct 2015 21:14:57 +0200 [thread overview]
Message-ID: <562FCD31.60508@cloudius-systems.com> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB97725836AB5A51@irsmsx105.ger.corp.intel.com>
On 10/27/15 21:10, Ananyev, Konstantin wrote:
> Hi lads,
>
>> -----Original Message-----
>> From: Vlad Zolotarov [mailto:vladz@cloudius-systems.com]
>> Sent: Tuesday, October 27, 2015 6:48 PM
>> To: Thomas Monjalon; Ananyev, Konstantin; Zhang, Helin
>> Cc: dev@dpdk.org; Kirsher, Jeffrey T; Brandeburg, Jesse
>> Subject: Re: [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598
>>
>>
>>
>> On 10/27/15 20:09, Thomas Monjalon wrote:
>>> Any Follow-up to this discussion?
>>> Should we mark this patch as rejected?
>> Hmmm... This patch fixes an obvious spec violation. Why would it be
>> rejected?
> No I don't think we can reject the patch:
> There is a reproducible TX hang on ixgbe PMD on described conditions.
> Though, as I explained here:
> http://dpdk.org/ml/archives/dev/2015-September/023574.html
> Vlad's patch would cause quite a big slowdown.
> We are still in the process to get an answer from HW guys are there any
> alternatives that will allow to fix the problem and avoid the slowdown.
+1
> Konstantin
>
>>> 2015-08-24 11:11, Vlad Zolotarov:
>>>> On 08/20/15 18:37, Vlad Zolotarov wrote:
>>>>> According to 82599 and x540 HW specifications RS bit *must* be
>>>>> set in the last descriptor of *every* packet.
>>>>>
>>>>> Before this patch there were 3 types of Tx callbacks that were setting
>>>>> RS bit every tx_rs_thresh descriptors. This patch introduces a set of
>>>>> new callbacks, one for each type mentioned above, that will set the RS
>>>>> bit in every EOP descriptor.
>>>>>
>>>>> ixgbe_set_tx_function() will set the appropriate Tx callback according
>>>>> to the device family.
>>>> [+Jesse and Jeff]
>>>>
>>>> I've started to look at the i40e PMD and it has the same RS bit
>>>> deferring logic
>>>> as ixgbe PMD has (surprise, surprise!.. ;)). To recall, i40e PMD uses a
>>>> descriptor write-back
>>>> completion mode.
>>>>
>>>> From the HW Spec it's unclear if RS bit should be set on *every* descriptor
>>>> with EOP bit. However I noticed that Linux driver, before it moved to
>>>> HEAD write-back mode, was setting RS
>>>> bit on every EOP descriptor.
>>>>
>>>> So, here is a question to Intel guys: could u, pls., clarify this point?
>>>>
>>>> Thanks in advance,
>>>> vlad
>>>
next prev parent reply other threads:[~2015-10-27 19:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-20 15:37 Vlad Zolotarov
2015-08-24 8:11 ` Vlad Zolotarov
2015-10-27 18:09 ` Thomas Monjalon
2015-10-27 18:47 ` Vlad Zolotarov
2015-10-27 18:50 ` Brandeburg, Jesse
2015-10-27 19:10 ` Ananyev, Konstantin
2015-10-27 19:14 ` Vlad Zolotarov [this message]
2015-11-09 19:21 ` [dpdk-dev] [PATCHv6 0/2] ixgbe: fix TX hang when RS distance exceeds HW limit Konstantin Ananyev
2015-11-09 19:21 ` [dpdk-dev] [PATCHv6 1/2] testpmd: add ability to split outgoing packets Konstantin Ananyev
2015-11-09 19:21 ` [dpdk-dev] [PATCHv6 2/2] ixgbe: fix TX hang when RS distance exceeds HW limit Konstantin Ananyev
2015-11-10 13:48 ` [dpdk-dev] [PATCHv7 0/2] " Konstantin Ananyev
2015-11-10 14:06 ` De Lara Guarch, Pablo
2015-11-11 23:15 ` Thomas Monjalon
2015-11-10 13:48 ` [dpdk-dev] [PATCHv7 1/2] testpmd: add ability to split outgoing packets Konstantin Ananyev
2015-11-10 13:48 ` [dpdk-dev] [PATCHv7 2/2] ixgbe: fix TX hang when RS distance exceeds HW limit Konstantin Ananyev
2015-09-11 16:26 [dpdk-dev] [PATCH v4] ixgbe_pmd: enforce RS bit on every EOP descriptor for devices newer than 82598 Konstantin Ananyev
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