Re: [dpdk-dev] Old oversubscription related checkin

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

Hi Sridhar,

I think this patch is simply the implementation of the oversubscription feature, as introduced by DPDK release 1.4.1. Most likely, this patch is the way Thomas added this Intel release to dpdk.org.

The oversubscription feature was never implemented for all 4 traffic classes. The patch you are pointing to simply introduced this feature for TC3 only. Before this patch, there might have been just a placeholder in the code for the oversubscription feature that was to be developed later on.

Again, the reason for introducing this feature for TC3 only is that the higher priority traffic classes TC0 .. TC2 are typically fully provisioned, as the amount of TC0 .. TC2 traffic is much less than TC3 (Best Effort) traffic, which is usually hugely overprovisioned. This feature can potentially be extended to TC0 .. TC2 as well, as the way this feature basically works is deciding the quanta to be applied for all pipes in the subport during the next scheduling decision based on the amount of unused credits found at the end of the current scheduling period.

Regards,
Cristian

From: Sridhar.V.Iyer [mailto:sridhariyer@versa-networks.com]
Sent: Wednesday, May 4, 2016 10:15 PM
To: dev@dpdk.org; Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
Cc: Ananda <ananda@versa-networks.com>
Subject: Old oversubscription related checkin

Hi Cristian,

 I stumbled into an old from 2013 (http://dpdk.org/browse/dpdk/patch/lib/librte_sched/rte_sched.c?id=835c5409a7bac3055b82bebee65d8ada7f20d332)

I couldn’t find any context for the patch from the mail archives. Could you please let me know why oversubscription was removed from all the other traffic classes and just given to tc3?
Were there huge performance penalties? Would there be any issues if I add this patch back again locally (enable/disabled via config).

Regards,

Sridhar V Iyer

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