[dpdk-dev] [PATCH 0/2] lib: add TCP IPv4 GRO support

Morten Brørup mb at smartsharesystems.com
Wed Mar 29 12:47:42 CEST 2017

I have two points to this discussion:

GRO/LRO must be disabled by default! Truly transparent network appliances, such as classic Layer 3 routers and Layer 2 switches (and our SmartShare StraightShaper appliance), may not want to merge multiple smaller packets into one larger packet, regardless of any processing performance benefit. Also refer to Wikipedia (https://en.wikipedia.org/wiki/Large_receive_offload), especially reference 9 (https://bugzilla.redhat.com/show_bug.cgi?id=772317). And if any of you developers don't intuitively agree, just ask any old network engineer about all the mess he had to deal with "back in the days" when packet sizes were important... flaky path MTU discovery, MSS clamping for PPPoE and VPN tunnels, packet reassembly causing performance degradation and packet loss on underpowered VPN routers, etc.

We should consider librte_net a library for miscellaneous utilities, i.e. mainly stateless functions. Functions for packet merging (of multiple IP packets or actual IP fragments), which clearly requires a lot of memory and statefulness, does not belong here. This is worth noting, not only for the GRO/GSO library, but for similar future discussions. (The size of the compiled library is irrelevant - only its purpose matters.)

Med venlig hilsen / kind regards

Morten Brørup

SmartShare Systems A/S
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mb at smartsharesystems.com

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