From: Florian Fainelli <f.fainelli@gmail.com>
To: Christian Eggers <ceggers@arri.de>, Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@gmail.com>,
Vladimir Oltean <olteanv@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
Kurt Kanzenbach <kurt@linutronix.de>
Cc: "David S . Miller" <davem@davemloft.net>,
Woojung Huh <woojung.huh@microchip.com>,
Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] net: dsa: move skb reallocation to dsa_slave_xmit
Date: Fri, 16 Oct 2020 19:44:37 -0700 [thread overview]
Message-ID: <9795d523-c296-cc18-4188-9214fb9cc25d@gmail.com> (raw)
In-Reply-To: <20201016200226.23994-1-ceggers@arri.de>
On 10/16/2020 1:02 PM, Christian Eggers wrote:
[snip]
> On Friday, 16 October 2020, 20:03:11 CEST, Jakub Kicinski wrote:
>> FWIW if you want to avoid the reallocs you may want to set
>> needed_tailroom on the netdev.
> I haven't looked for this yet. If this can really solve the tagging AND
> padding problem, I would like to do this in a follow up patch.
The comment in netdevice.h says:
* @needed_headroom: Extra headroom the hardware may need, but
not in all
* cases can this be guaranteed
* @needed_tailroom: Extra tailroom the hardware may need, but
not in all
* cases can this be guaranteed. Some cases
also use
* LL_MAX_HEADER instead to allocate the skb
and while I have never seen a reallocation occur while pushing a
descriptor status block in front of a frame on transmit after setting
the correct needed_headroom, it was not exercised in a very complicated
way either, just TCP or UDP over IPv4 or IPv6. This makes me think that
the comment is cautionary about more complicated transmit scenarios with
stacked devices, tunneling etc.
>
> Wishing a nice weekend for netdev.
Likewise!
--
Florian
prev parent reply other threads:[~2020-10-17 6:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 20:02 [PATCH 0/3] net: dsa: move skb reallocation to dsa_slave_xmit Christian Eggers
2020-10-16 20:02 ` [PATCH net-next 1/3] net: dsa: don't pass cloned skb's to drivers xmit function Christian Eggers
2020-10-17 0:48 ` Vladimir Oltean
2020-10-17 18:53 ` Christian Eggers
2020-10-17 19:12 ` Vladimir Oltean
2020-10-17 20:56 ` Christian Eggers
2020-10-17 21:35 ` Vladimir Oltean
2020-10-17 2:35 ` Florian Fainelli
2020-10-16 20:02 ` [PATCH net-next 2/3] net: dsa: tag_ksz: don't allocate additional memory for padding/tagging Christian Eggers
2020-10-16 20:02 ` [PATCH net-next 3/3] net: dsa: trailer: " Christian Eggers
2020-10-17 2:44 ` Florian Fainelli [this message]
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