From: Roland Dreier <rdreier@cisco.com>
To: David Miller <davem@davemloft.net>
Cc: mst@mellanox.co.il, shemminger@osdl.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
openib-general@openib.org, rolandd@cisco.com
Subject: Re: Dropping NETIF_F_SG since no checksum feature.
Date: Tue, 10 Oct 2006 20:42:20 -0700 [thread overview]
Message-ID: <adak637bjs3.fsf@cisco.com> (raw)
In-Reply-To: <20061010.203624.91207079.davem@davemloft.net> (David Miller's message of "Tue, 10 Oct 2006 20:36:24 -0700 (PDT)")
David> Also, if you don't do checksumming on the card we MUST copy
David> the data (be it from a user buffer, or from a filesystem
David> page cache page) into a private buffer since if the data
David> changes the checksum would become invalid, as I mentioned
David> in another email earlier.
Yes, I get that now -- I replied to Michael's email before I read yours.
David> Therefore, since we have to copy anyways, it always is
David> better to checksum in parallel with the copy.
Yes.
David> So the whole idea of SG without hw-checksum support is
David> without much merit at all.
Well, on IB it is possible to implement a netdevice (IPoIB connected
mode, I assume that's what Michael is working on) with a large MTU
(64KB is a number thrown around, but really there's not any limit) but
no HW checksum capability. Doing that in a practical way means we
need to allow non-linear skbs to be passed in.
On the other hand I'm not sure how useful such a netdevice would be --
will non-sendfile() paths generate big packets even if the MTU is 64KB?
Maybe GSO gives us all the real advantages of this anyway?
- R.
next prev parent reply other threads:[~2006-10-11 3:42 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-09 17:47 Dropping NETIF_F_SG since no checksum feature Michael S. Tsirkin
2006-10-09 16:50 ` Stephen Hemminger
2006-10-09 16:50 ` Stephen Hemminger
2006-10-10 14:43 ` Michael S. Tsirkin
2006-10-10 17:43 ` Stephen Hemminger
2006-10-11 0:13 ` Michael S. Tsirkin
2006-10-11 0:15 ` Roland Dreier
2006-10-11 0:26 ` Michael S. Tsirkin
2006-10-11 3:33 ` Roland Dreier
2006-10-11 3:36 ` David Miller
2006-10-11 3:42 ` Roland Dreier [this message]
2006-10-11 3:45 ` David Miller
2006-10-11 3:49 ` Roland Dreier
2006-10-11 3:50 ` David Miller
2006-10-11 2:15 ` David Miller
2006-10-11 9:05 ` Michael S. Tsirkin
2006-10-11 9:05 ` Michael S. Tsirkin
2006-10-11 9:09 ` Steven Whitehouse
2006-10-11 15:01 ` Michael S. Tsirkin
2006-10-11 20:11 ` Steven Whitehouse
2006-10-11 20:52 ` Michael S. Tsirkin
2006-10-11 20:57 ` Stephen Hemminger
2006-10-11 21:23 ` Michael S. Tsirkin
2006-10-11 21:23 ` Michael S. Tsirkin
2006-10-11 21:29 ` Stephen Hemminger
2006-10-11 21:42 ` Michael S. Tsirkin
2006-10-11 21:41 ` David Miller
2006-10-12 19:12 ` Michael S. Tsirkin
2006-10-12 19:12 ` Michael S. Tsirkin
2006-10-13 4:22 ` David Miller
2006-10-13 6:17 ` Michael S. Tsirkin
2006-10-11 20:52 ` David Miller
2006-10-11 20:52 ` David Miller
2006-10-11 21:11 ` Michael S. Tsirkin
2006-10-11 21:11 ` Michael S. Tsirkin
2006-10-11 9:20 ` David Miller
2006-10-11 9:46 ` Michael S. Tsirkin
2006-10-11 18:21 ` [openib-general] " Michael Krause
2006-10-11 13:11 ` [RFC] Question about potential problem in net/ipv4/route.c Eric Dumazet
2006-10-12 5:05 ` David Miller
2006-10-12 5:31 ` Patrick McHardy
2006-10-12 5:54 ` David Miller
2006-10-12 5:48 ` Eric Dumazet
2006-10-12 6:02 ` David Miller
2006-10-12 6:10 ` Patrick McHardy
2006-10-12 6:25 ` David Miller
2006-10-12 6:35 ` Eric Dumazet
2006-10-12 7:48 ` David Miller
2006-10-16 9:00 ` [PATCH] NET : Suspicious locking in reqsk_queue_hash_req() Eric Dumazet
2006-10-16 9:07 ` Eric Dumazet
2006-10-16 16:16 ` Arnaldo Carvalho de Melo
2006-10-16 16:56 ` Eric Dumazet
2006-10-16 17:39 ` Eric Dumazet
2006-10-16 20:41 ` David Miller
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