From: David Miller <davem@davemloft.net>
To: jakub.kicinski@netronome.com
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH v4 net-next 01/15] nfp: correct RX buffer length calculation
Date: Tue, 05 Apr 2016 11:39:17 -0400 (EDT) [thread overview]
Message-ID: <20160405.113917.846241936652070162.davem@davemloft.net> (raw)
In-Reply-To: <1459544811-24879-2-git-send-email-jakub.kicinski@netronome.com>
From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Fri, 1 Apr 2016 22:06:37 +0100
> When calculating the RX buffer length we need to account for
> up to 2 VLAN tags and up to 8 MPLS labels. Rounding up to 1k
> is an relic of a distant past and can be removed. While at
> it also remove trivial print statement.
>
> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
I disagree with the MPLS aspect of this change.
VLAN is special, in that when the hardware supports VLAN properly, the
VLAN header doesn't eat into the MTU and is sort of "transparent".
But MPLS doesn't work that way.
MPLS is in the main frame and takes up MTU space.
Therefore I see no reason to increase the buffer length by 8 * MPLS
which is just a rediculous amount of wasted space.
I'm not applying this without at least some more explanations about
why exactly you need to account for these values in the commit message.
next prev parent reply other threads:[~2016-04-05 15:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 21:06 [PATCH v4 net-next 00/15] MTU/buffer reconfig changes Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 01/15] nfp: correct RX buffer length calculation Jakub Kicinski
2016-04-05 15:39 ` David Miller [this message]
2016-04-05 17:24 ` Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 02/15] nfp: move link state interrupt request/free calls Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 03/15] nfp: break up nfp_net_{alloc|free}_rings Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 04/15] nfp: make *x_ring_init do all the init Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 05/15] nfp: allocate ring SW structs dynamically Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 06/15] nfp: cleanup tx ring flush and rename to reset Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 07/15] nfp: reorganize initial filling of RX rings Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 08/15] nfp: preallocate RX buffers early in .ndo_open Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 09/15] nfp: move filling ring information to FW config Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 10/15] nfp: slice .ndo_open() and .ndo_stop() up Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 11/15] nfp: sync ring state during FW reconfiguration Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 12/15] nfp: propagate list buffer size in struct rx_ring Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 13/15] nfp: convert .ndo_change_mtu() to prepare/commit paradigm Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 14/15] nfp: pass ring count as function parameter Jakub Kicinski
2016-04-01 21:06 ` [PATCH v4 net-next 15/15] nfp: allow ring size reconfiguration at runtime Jakub Kicinski
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