On Wed, Aug 19, 2015 at 09:00:52AM +0200, Hans Petter Selasky wrote: > On 08/18/15 23:54, Rick Macklem wrote: > >Ouch! Yes, I now see that the code that counts the # of mbufs is before the > >code that adds the tcp/ip header mbuf. > > > >In my opinion, this should be fixed by setting if_hw_tsomaxsegcount to > >whatever > >the driver provides - 1. It is not the driver's responsibility to know if > >a tcp/ip > >header mbuf will be added and is a lot less confusing that expecting the > >driver > >author to know to subtract one. (I had mistakenly thought that > >tcp_output() had > >added the tc/ip header mbuf before the loop that counts mbufs in the list. > >Btw, > >this tcp/ip header mbuf also has leading space for the MAC layer header.) > > > > Hi Rick, > > Your question is good. With the Mellanox hardware we have separate > so-called inline data space for the TCP/IP headers, so if the TCP stack > subtracts something, then we would need to add something to the limit, > because then the scatter gather list is only used for the data part. >
I think all drivers in tree don't subtract 1 for if_hw_tsomaxsegcount. Probably touching Mellanox driver would be simpler than fixing all other drivers in tree. > Maybe it can be controlled by some kind of flag, if all the three TSO > limits should include the TCP/IP/ethernet headers too. I'm pretty sure > we want both versions. > Hmm, I'm afraid it's already complex. Drivers have to tell almost the same information to both bus_dma(9) and network stack. _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
