From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] select appropriate skb size in tcp_sendmsg when TSO is used Date: Thu, 28 Oct 2004 00:16:33 -0400 Sender: netdev-bounce@oss.sgi.com Message-ID: <418072A1.9020509@pobox.com> References: <20041020163510.6d13e9c7.davem@davemloft.net> <20041026111912.GA18095@gondor.apana.org.au> <20041026235126.GA4733@gondor.apana.org.au> <417EE3BB.6040902@pobox.com> <20041027000724.GA4869@gondor.apana.org.au> <20041027001531.GA29973@havoc.gtf.org> <20041027002209.GA5002@gondor.apana.org.au> <20041026175553.55a1b72d.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: Herbert Xu , thomas.spatzier@de.ibm.com, netdev@oss.sgi.com Return-path: To: "David S. Miller" In-Reply-To: <20041026175553.55a1b72d.davem@davemloft.net> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org David S. Miller wrote: > On Wed, 27 Oct 2004 10:22:09 +1000 > Herbert Xu wrote: > > >>On Tue, Oct 26, 2004 at 08:15:31PM -0400, Jeff Garzik wrote: >> >>>>IMHO it is valid to disable SG without disabling checksums, no? >>> >>>It's useless: The packet header is always in a separate memory >>>location from the packet data, when using zerocopy sendfile(2). >>> >>>When not using zerocopy sendfile, you are copying the data _anyway_. >> >>I'm fine with adding this check. However I think that belongs in >>another patch since we don't check that in register_netdev currently. >> >>Dave, what do you think? > > > I believe that allowing TX csum support without SG _is_ > useful even though it is not _effective_. > > It is quite desirable for a driver author to be able to > test out his TX csum offload support first, then add > SG support next. Similarly, if a driver author suspects > some issues with either SG or TX csum support, he can > better isolate the problem if we allow this. > > Jeff do you agree? it's never used that way in practice AFAIK, only used by confused sysadmins :) I won't object if you preserve the behavior, but I still don't see much value in allowing it. Jeff