Re: [PATCH 5.4 086/129] net: core: use listified Rx for GRO_NORMAL in napi_gro_receive()

From: Edward Cree
Date: Tue Sep 08 2020 - 17:35:40 EST

On 08/09/2020 16:25, Greg Kroah-Hartman wrote:
> From: Alexander Lobakin <alobakin@xxxxxxxx>
> commit 6570bc79c0dfff0f228b7afd2de720fb4e84d61d upstream.
> Commit 323ebb61e32b4 ("net: use listified RX for handling GRO_NORMAL
> skbs") made use of listified skb processing for the users of
> napi_gro_frags().
> The same technique can be used in a way more common napi_gro_receive()
> to speed up non-merged (GRO_NORMAL) skbs for a wide range of drivers
> including gro_cells and mac80211 users.
> This slightly changes the return value in cases where skb is being
> dropped by the core stack, but it seems to have no impact on related
> drivers' functionality.
> gro_normal_batch is left untouched as it's very individual for every
> single system configuration and might be tuned in manual order to
> achieve an optimal performance.
> Signed-off-by: Alexander Lobakin <alobakin@xxxxxxxx>
> Acked-by: Edward Cree <ecree@xxxxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Hyunsoon Kim <>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
I'm not quite sure why this is stable material(it's a performance
 enhancement, rather than a fix).  But if you do want to take it,
 make sure you've also got
c80794323e82 ("net: Fix packet reordering caused by GRO and listified RX cooperation")
b167191e2a85 ("net: wireless: intel: iwlwifi: fix GRO_NORMAL packet stalling")
 in your tree, particularly the latter as without it this commit
 triggers a severe regression in iwlwifi.