On 10/27/15 21:10, Ananyev, Konstantin wrote: > Hi lads, > >> -----Original Message----- >> From: Vlad Zolotarov [mailto:vladz at cloudius-systems.com] >> Sent: Tuesday, October 27, 2015 6:48 PM >> To: Thomas Monjalon; Ananyev, Konstantin; Zhang, Helin >> Cc: dev at 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 >>>
