sfxge: Separate software Tx queue limit for non-TCP traffic

Add separate software Tx queue limit for non-TCP traffic to make total
limit higher and avoid local drops of TCP packets because of no
backpressure.
There is no point to make non-TCP limit high since without backpressure
UDP stream easily overflows any sensible limit.

Split early drops statistics since it is better to have separate counter
for each drop reason to make it unabmiguous.

Add software Tx queue high watermark. The information is very useful to
understand how big queues grow under traffic load.

Sponsored by:   Solarflare Communications, Inc.
Approved by:    gnn (mentor)

1 files changed, 12 insertions, 4 deletions

diff --git a/share/man/man4/sfxge.4 b/share/man/man4/sfxge.4
index e4b0b94..9b6025d 100644
--- a/share/man/man4/sfxge.4
+++ b/share/man/man4/sfxge.4
@@ -93,10 +93,18 @@ Supported values are: 512, 1024, 2048 and 4096.
 .It Va hw.sfxge.tx_dpl_get_max
 The maximum length of the deferred packet
 .Dq get-list
-for queued transmit
-packets, used only if the transmit queue lock can be acquired.
+for queued transmit packets (TCP and non-TCP), used only if the transmit
+queue lock can be acquired.
 If a packet is dropped, the
-.Va tx_early_drops
+.Va tx_get_overflow
+counter is incremented and the local sender receives ENOBUFS.
+The value must be greater than 0.
+.It Va hw.sfxge.tx_dpl_get_non_tcp_max
+The maximum number of non-TCP packets in the deferred packet
+.Dq get-list
+, used only if the transmit queue lock can be acquired.
+If packet is dropped, the
+.Va tx_get_non_tcp_overflow
 counter is incremented and the local sender receives ENOBUFS.
 The value must be greater than 0.
 .It Va hw.sfxge.tx_dpl_put_max
@@ -105,7 +113,7 @@ The maximum length of the deferred packet
 for queued transmit
 packets, used if the transmit queue lock cannot be acquired.
 If a packet is dropped, the
-.Va tx_early_drops
+.Va tx_put_overflow
 counter is incremented and the local sender receives ENOBUFS.
 The value must be greater than or equal to 0.
 .It Va hw.sfxge.N.max_rss_channels