git: c81f8c26115a - main - ena: Avoid unnecessary mbuf collapses for LLQ condition

[Marcin Wojtas]

The branch main has been updated by mw:

URL: https://cgit.FreeBSD.org/src/commit/?id=c81f8c26115a64b9a97ecdb2a64e824dd839ee73

commit c81f8c26115a64b9a97ecdb2a64e824dd839ee73
Author:     Artur Rojek <ar at semihalf.com>
AuthorDate: 2021-08-12 08:34:17 +0000
Commit:     Marcin Wojtas <mw at FreeBSD.org>
CommitDate: 2021-09-01 23:05:38 +0000

    ena: Avoid unnecessary mbuf collapses for LLQ condition
    
    In case of Low-latency Queue, one small enough descriptor can be pushed
    directly to the ENA hw, thus saving one fragment. Check for this
    condition before performing collapse.
    
    Obtained from: Semihalf
    MFC after: 2 weeks
    Sponsored by: Amazon, Inc.
---
 sys/dev/ena/ena_datapath.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sys/dev/ena/ena_datapath.c b/sys/dev/ena/ena_datapath.c
index 15bd09c489cf..c0066b1209cc 100644
--- a/sys/dev/ena/ena_datapath.c
+++ b/sys/dev/ena/ena_datapath.c
@@ -801,6 +801,11 @@ ena_check_and_collapse_mbuf(struct ena_ring *tx_ring, struct mbuf **mbuf)
 	/* One segment must be reserved for configuration descriptor. */
 	if (num_frags < adapter->max_tx_sgl_size)
 		return (0);
+
+	if ((num_frags == adapter->max_tx_sgl_size) &&
+	    ((*mbuf)->m_pkthdr.len < tx_ring->tx_max_header_size))
+		return (0);
+
 	counter_u64_add(tx_ring->tx_stats.collapse, 1);
 
 	collapsed_mbuf = m_collapse(*mbuf, M_NOWAIT,