Author: arybchik Date: Tue Jan 10 16:25:39 2017 New Revision: 311877 URL: https://svnweb.freebsd.org/changeset/base/311877
Log: sfxge(4): avoid unnecessary mbuf data prefetch Unnecessary prefetch just loads HW prefetcher and displaces other cache entries (which could be really useful). If we parse mbuf for TSO early and use firmware-assisted TSO, we do not expect mbuf data access when we compose firmware-assisted TSO (v1 or v2) option descriptors. If packet header needs to be linearized or finally FATSO cannot be used because of, for example, too big header, we do not care about a bit more performance degradation because of prefetch absence (it is better to optimize more common case). Reviewed by: gnn Sponsored by: Solarflare Communications, Inc. MFC after: 2 days Differential Revision: https://reviews.freebsd.org/D9120 Modified: head/sys/dev/sfxge/sfxge_tx.c Modified: head/sys/dev/sfxge/sfxge_tx.c ============================================================================== --- head/sys/dev/sfxge/sfxge_tx.c Tue Jan 10 14:40:30 2017 (r311876) +++ head/sys/dev/sfxge/sfxge_tx.c Tue Jan 10 16:25:39 2017 (r311877) @@ -363,8 +363,22 @@ static int sfxge_tx_queue_mbuf(struct sf KASSERT(!txq->blocked, ("txq->blocked")); +#if SFXGE_TX_PARSE_EARLY + /* + * If software TSO is used, we still need to copy packet header, + * even if we have already parsed it early before enqueue. + */ + if ((mbuf->m_pkthdr.csum_flags & CSUM_TSO) && + (txq->tso_fw_assisted == 0)) + prefetch_read_many(mbuf->m_data); +#else + /* + * Prefetch packet header since we need to parse it and extract + * IP ID, TCP sequence number and flags. + */ if (mbuf->m_pkthdr.csum_flags & CSUM_TSO) prefetch_read_many(mbuf->m_data); +#endif if (__predict_false(txq->init_state != SFXGE_TXQ_STARTED)) { rc = EINTR; _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
