14.09.2015, 11:36, "Hans Petter Selasky" <hsela...@freebsd.org>: > Author: hselasky > Date: Mon Sep 14 08:36:22 2015 > New Revision: 287775 > URL: https://svnweb.freebsd.org/changeset/base/287775 > > Log: > Update TSO limits to include all headers. > > To make driver programming easier the TSO limits are changed to > reflect the values used in the BUSDMA tag a network adapter driver is > using. The TCP/IP network stack will subtract space for all linklevel > and protocol level headers and ensure that the full mbuf chain passed > to the network adapter fits within the given limits. > > Implementation notes: > > If a network adapter driver needs to fixup the first mbuf in order to > support VLAN tag insertion, the size of the VLAN tag should be > subtracted from the TSO limit. Else not. > > Network adapters which typically inline the complete header mbuf could > technically transmit one more segment. This patch does not implement a > mechanism to recover the last segment for data transmission. It is > believed when sufficiently large mbuf clusters are used, the segment > limit will not be reached and recovering the last segment will not > have any effect. > > The current TSO algorithm tries to send MTU-sized packets, where the > MTU typically is 1500 bytes, which gives 1448 bytes of TCP data > payload per packet for IPv4. That means if the TSO length limitiation > is set to 65536 bytes, there will be a data payload remainder of > (65536 - 1500) mod 1448 bytes which is equal to 324 bytes. Trying to > recover total TSO length due to inlining mbuf header data will not > have any effect, because adding or removing the ETH/IP/TCP headers > to or from 324 bytes will not cause more or less TCP payload to be > TSO'ed. > > Existing network adapter limits will be updated separately. > > Differential Revision: https://reviews.freebsd.org/D3458 Probably different revision id ?
> Reviewed by: rmacklem > MFC after: 2 weeks > > Modified: > head/sys/net/if_var.h > head/sys/netinet/tcp_output.c > > Modified: head/sys/net/if_var.h > ============================================================================== > --- head/sys/net/if_var.h Mon Sep 14 08:01:05 2015 (r287774) > +++ head/sys/net/if_var.h Mon Sep 14 08:36:22 2015 (r287775) > @@ -243,11 +243,12 @@ struct ifnet { > * count limit does not apply. If all three fields are zero, > * there is no TSO limit. > * > - * NOTE: The TSO limits only apply to the data payload part of > - * a TCP/IP packet. That means there is no need to subtract > - * space for ethernet-, vlan-, IP- or TCP- headers from the > - * TSO limits unless the hardware driver in question requires > - * so. > + * NOTE: The TSO limits should reflect the values used in the > + * BUSDMA tag a network adapter is using to load a mbuf chain > + * for transmission. The TCP/IP network stack will subtract > + * space for all linklevel and protocol level headers and > + * ensure that the full mbuf chain passed to the network > + * adapter fits within the given limits. > */ > u_int if_hw_tsomax; /* TSO maximum size in bytes */ > u_int if_hw_tsomaxsegcount; /* TSO maximum segment count */ > > Modified: head/sys/netinet/tcp_output.c > ============================================================================== > --- head/sys/netinet/tcp_output.c Mon Sep 14 08:01:05 2015 (r287774) > +++ head/sys/netinet/tcp_output.c Mon Sep 14 08:36:22 2015 (r287775) > @@ -811,7 +811,8 @@ send: > */ > if (if_hw_tsomax != 0) { > /* compute maximum TSO length */ > - max_len = (if_hw_tsomax - hdrlen); > + max_len = (if_hw_tsomax - hdrlen - > + max_linkhdr); > if (max_len <= 0) { > len = 0; > } else if (len > max_len) { > @@ -826,6 +827,15 @@ send: > */ > if (if_hw_tsomaxsegcount != 0 && > if_hw_tsomaxsegsize != 0) { > + /* > + * Subtract one segment for the LINK > + * and TCP/IP headers mbuf that will > + * be prepended to this mbuf chain > + * after the code in this section > + * limits the number of mbufs in the > + * chain to if_hw_tsomaxsegcount. > + */ > + if_hw_tsomaxsegcount -= 1; > max_len = 0; > mb = sbsndmbuf(&so->so_snd, off, &moff); _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"