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Subject: Re: [PATCH 5.4 086/129] net: core: use listified Rx for GRO_NORMAL in
 napi_gro_receive()
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        <linux-kernel@vger.kernel.org>
CC:     <stable@vger.kernel.org>, Alexander Lobakin <alobakin@dlink.ru>,
        "David S. Miller" <davem@davemloft.net>,
        Hyunsoon Kim <h10.kim@samsung.com>
References: <20200908152229.689878733@linuxfoundation.org>
 <20200908152234.000867723@linuxfoundation.org>
From:   Edward Cree <ecree@solarflare.com>
Message-ID: <70529b6c-7b00-d760-c0c0-42f0ea5784f3@solarflare.com>
Date:   Tue, 8 Sep 2020 22:35:22 +0100
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On 08/09/2020 16:25, Greg Kroah-Hartman wrote:
> From: Alexander Lobakin <alobakin@dlink.ru>
>
> 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@dlink.ru>
> Acked-by: Edward Cree <ecree@solarflare.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Hyunsoon Kim <h10.kim@samsung.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.

-ed