Based on various feedback, on my RH Linux 2.4.18 kernel I tried the following: Set "features" bit NETIF_F_IP_CSUM set (the only feature bit set). In my network driver start-transmit check for "CHECKSUM_HW" in ip_summed. Using a small test program, use "sendfile" to copy a file to a network socket FD. Result is none of the packets presented to my network adapter driver have ip_summed set to CHECKSUM_HW, so the SW IP stack has already computed checksums. Is this mechanism possibly broken on kernel 2.4? "Jeff Garzik" <jgarzik@pobox.com> wrote in message 20030402205855.GA4125@gtf.org">news:20030402205855.GA4125@gtf.org... > On Wed, Apr 02, 2003 at 03:47:35PM -0500, Dennis Cook wrote: > > What I was looking for is a general capability to keep the SW transport > > stack from > > computing outgoing TCP/UDP/IP checksums so that the HW can be allowed to do > > it, > > similar to Windows checksum offload capability. > > If you are not using sendfile(2), it is _more expensive_ to offload > checksums, because we already checksum and copy at the same time. > > Hardware checksum offload is only a win when a copy is eliminated. > > Therefore, _always_ offloading checksum is actually slower in some > cases, because of the unneeded additional HW csum setup that would be > performed. > > Jeff > > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
