Author: sbruno Date: Thu Jan 7 16:48:47 2016 New Revision: 293332 URL: https://svnweb.freebsd.org/changeset/base/293332
Log: Disable the reuse of checksum offload context descriptors in the case of multiple queues in em(4). Document errata in the code. MFC after: 2 weeks Sponsored by: Limelight Networks Differential Revision: https://reviews.freebsd.org/D3995 Modified: head/sys/dev/e1000/if_em.c Modified: head/sys/dev/e1000/if_em.c ============================================================================== --- head/sys/dev/e1000/if_em.c Thu Jan 7 16:42:48 2016 (r293331) +++ head/sys/dev/e1000/if_em.c Thu Jan 7 16:48:47 2016 (r293332) @@ -3735,29 +3735,38 @@ em_transmit_checksum_setup(struct tx_rin offload |= CSUM_TCP; tucss = hdr_len; tucso = hdr_len + offsetof(struct tcphdr, th_sum); - /* - * Setting up new checksum offload context for every frames - * takes a lot of processing time for hardware. This also - * reduces performance a lot for small sized frames so avoid - * it if driver can use previously configured checksum - * offload context. - */ - if (txr->last_hw_offload == offload) { - if (offload & CSUM_IP) { - if (txr->last_hw_ipcss == ipcss && - txr->last_hw_ipcso == ipcso && - txr->last_hw_tucss == tucss && - txr->last_hw_tucso == tucso) - return; - } else { - if (txr->last_hw_tucss == tucss && - txr->last_hw_tucso == tucso) - return; - } - } - txr->last_hw_offload = offload; - txr->last_hw_tucss = tucss; - txr->last_hw_tucso = tucso; + /* + * The 82574L can only remember the *last* context used + * regardless of queue that it was use for. We cannot reuse + * contexts on this hardware platform and must generate a new + * context every time. 82574L hardware spec, section 7.2.6, + * second note. + */ + if (adapter->num_queues < 2) { + /* + * Setting up new checksum offload context for every + * frames takes a lot of processing time for hardware. + * This also reduces performance a lot for small sized + * frames so avoid it if driver can use previously + * configured checksum offload context. + */ + if (txr->last_hw_offload == offload) { + if (offload & CSUM_IP) { + if (txr->last_hw_ipcss == ipcss && + txr->last_hw_ipcso == ipcso && + txr->last_hw_tucss == tucss && + txr->last_hw_tucso == tucso) + return; + } else { + if (txr->last_hw_tucss == tucss && + txr->last_hw_tucso == tucso) + return; + } + } + txr->last_hw_offload = offload; + txr->last_hw_tucss = tucss; + txr->last_hw_tucso = tucso; + } /* * Start offset for payload checksum calculation. * End offset for payload checksum calculation. @@ -3773,29 +3782,38 @@ em_transmit_checksum_setup(struct tx_rin *txd_upper |= E1000_TXD_POPTS_TXSM << 8; tucss = hdr_len; tucso = hdr_len + offsetof(struct udphdr, uh_sum); - /* - * Setting up new checksum offload context for every frames - * takes a lot of processing time for hardware. This also - * reduces performance a lot for small sized frames so avoid - * it if driver can use previously configured checksum - * offload context. - */ - if (txr->last_hw_offload == offload) { - if (offload & CSUM_IP) { - if (txr->last_hw_ipcss == ipcss && - txr->last_hw_ipcso == ipcso && - txr->last_hw_tucss == tucss && - txr->last_hw_tucso == tucso) - return; - } else { - if (txr->last_hw_tucss == tucss && - txr->last_hw_tucso == tucso) - return; + /* + * The 82574L can only remember the *last* context used + * regardless of queue that it was use for. We cannot reuse + * contexts on this hardware platform and must generate a new + * context every time. 82574L hardware spec, section 7.2.6, + * second note. + */ + if (adapter->num_queues < 2) { + /* + * Setting up new checksum offload context for every + * frames takes a lot of processing time for hardware. + * This also reduces performance a lot for small sized + * frames so avoid it if driver can use previously + * configured checksum offload context. + */ + if (txr->last_hw_offload == offload) { + if (offload & CSUM_IP) { + if (txr->last_hw_ipcss == ipcss && + txr->last_hw_ipcso == ipcso && + txr->last_hw_tucss == tucss && + txr->last_hw_tucso == tucso) + return; + } else { + if (txr->last_hw_tucss == tucss && + txr->last_hw_tucso == tucso) + return; + } } - } - txr->last_hw_offload = offload; - txr->last_hw_tucss = tucss; - txr->last_hw_tucso = tucso; + txr->last_hw_offload = offload; + txr->last_hw_tucss = tucss; + txr->last_hw_tucso = tucso; + } /* * Start offset for header checksum calculation. * End offset for header checksum calculation. _______________________________________________ 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"
