netdev - Re: [RFC PATCH net-next] pktgen: Introducing a parameter for non-shared skb testing

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Date: Wed, 6 Sep 2023 18:32:17 -0400
From: Benjamin Poirier <benjamin.poirier@...il.com>
To: Liang Chen <liangchen.linux@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next] pktgen: Introducing a parameter for
 non-shared skb testing

On 2023-09-06 18:35 +0800, Liang Chen wrote:
> Currently, skbs generated by pktgen always have their reference count
> incremented before transmission, leading to two issues:
>   1. Only the code paths for shared skbs can be tested.
>   2. Skbs can only be released by pktgen.
> To enhance testing comprehensiveness, introducing the "skb_single_user"
> parameter, which allows skbs with a reference count of 1 to be
> transmitted. So we can test non-shared skbs and code paths where skbs
> are released within the network stack.

If my understanding of the code is correct, pktgen operates in the same
way with parameter clone_skb = 0 and clone_skb = 1.

clone_skb = 0 is already meant to work on devices that don't support
shared skbs (see IFF_TX_SKB_SHARING check in pktgen_if_write()). Instead
of introducing a new option for your purpose, how about changing
pktgen_xmit() to send "not shared" skbs when clone_skb == 0?

Note that for devices without IFF_TX_SKB_SHARING, it would no longer be
possible to have pktgen free skbs. Is that important?