From: David Miller <davem@davemloft.net>
To: rdreier@cisco.com
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 20:36:24 -0700 (PDT) [thread overview]
Message-ID: <20061010.203624.91207079.davem@davemloft.net> (raw)
In-Reply-To: <adar6xfbk6d.fsf@cisco.com>
From: Roland Dreier <rdreier@cisco.com>
Date: Tue, 10 Oct 2006 20:33:46 -0700
> Michael> My guess was, an extra pass over data is likely to be
> Michael> expensive - dirtying the cache if nothing else. But I do
> Michael> plan to measure that, and see.
>
> I don't get it -- where's the extra pass? If you can't compute the
> checksum on the NIC then you have to compute sometime it on the CPU
> before passing the data to the NIC.
Also, if you don't do checksumming on the card we MUST copy
the data (be it from a user buffer, or from a filesystem page
cache page) into a private buffer since if the data changes
the checksum would become invalid, as I mentioned in another
email earlier.
Therefore, since we have to copy anyways, it always is better
to checksum in parallel with the copy.
So the whole idea of SG without hw-checksum support is without
much merit at all.
next prev parent reply other threads:[~2006-10-11 3:36 UTC|newest]
Thread overview: 48+ 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
2006-10-10 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 [this message]
2006-10-11 3:42 ` Roland Dreier
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 9:09 ` 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 21:29 ` 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
2006-10-13 4:22 ` David Miller
2006-10-13 6:17 ` Michael S. Tsirkin
2006-10-11 20:52 ` David Miller
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20061010.203624.91207079.davem@davemloft.net \
--to=davem@davemloft.net \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@mellanox.co.il \
--cc=netdev@vger.kernel.org \
--cc=openib-general@openib.org \
--cc=rdreier@cisco.com \
--cc=rolandd@cisco.com \
--cc=shemminger@osdl.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).