igc: count TSO wire segments in the AIM counters

The transmit path bills one packet of ipi_len bytes per request.  For
TSO that is the whole unsegmented payload, up to 64 KiB, rather than a
packet size that appears on the wire.

Count the segments the hardware emits and the header carried by each
segment.  Non-TSO accounting is unchanged.

MFC after:	1 week

1 files changed, 19 insertions, 2 deletions

diff --git a/sys/dev/igc/igc_txrx.c b/sys/dev/igc/igc_txrx.c
index 12b6f2c43c39..0f88a0a5acd5 100644
--- a/sys/dev/igc/igc_txrx.c
+++ b/sys/dev/igc/igc_txrx.c
@@ -317,10 +317,27 @@ igc_isc_txd_encap(void *arg, if_pkt_info_t pi)
 	txd->read.cmd_type_len |= htole32(IGC_ADVTXD_DCMD_EOP | txd_flags);
 	pi->ipi_new_pidx = i;
 
-	/* Sent data accounting for AIM */
+	/*
+	 * Sent data accounting for AIM.  For TSO, ipi_len is the whole
+	 * unsegmented payload, which is not a size the moderation calculation
+	 * can use.  Count the segments the hardware will put on the wire and
+	 * the header each of them carries, so that the average it sees is a
+	 * wire packet.
+	 */
+	if ((pi->ipi_csum_flags & CSUM_TSO) && pi->ipi_tso_segsz != 0) {
+		u32 hdrlen, segs;
+
+		hdrlen = pi->ipi_ehdrlen + pi->ipi_ip_hlen + pi->ipi_tcp_hlen;
+		if (pi->ipi_len > hdrlen) {
+			segs = howmany(pi->ipi_len - hdrlen, pi->ipi_tso_segsz);
+			txr->tx_bytes += pi->ipi_len + (segs - 1) * hdrlen;
+			txr->tx_packets += segs;
+			return (0);
+		}
+	}
+
 	txr->tx_bytes += pi->ipi_len;
 	++txr->tx_packets;
-
 	return (0);
 }