On Tue, Apr 21, 2026 at 02:10:26PM +0200, Jan Klemkow wrote:
> On Tue, Apr 21, 2026 at 03:06:47PM +1000, David Gwynne wrote:
> > i thought it was weird that an MI driver like ix(4) is using an MD
> > number like PAGE_SIZE for the maximum segment size in its tx dma
> > maps.  the manual says tx segments can be 16k (and goes into a 16bit
> > field), so let's try using the documented value here.
> > 
> > the rx descs also use 16 * 1024 as a magic number here, so it's in
> > keeping with other code in the same driver.
> > 
> > ive only tested this on an Intel 82599 rev 0x01 on arm64, so tests
> > from other chips and sparc64 (which has an 8k page size) would be
> > appreciated.
> 
> works in my setups
> 
> ok jan@

cool, thanks.

we dusted a t4-1 with ix(4) inside off and tried it out. the
ix1:0:ix-txq:1 and ix1:0:txq:1 stats seem to show the stack pushing
large packets on to the hardware compared to what the hardware puts
on the wire, so im assuming large clusters made it into the transmit
path.

dlg@t4-1 ~$ netstat -m
748 mbufs in use:
	740 mbufs allocated to data
	1 mbuf allocated to packet headers
	7 mbufs allocated to socket names and addresses
0/80 mbuf 2048 byte clusters in use (current/peak)
553/1185 mbuf 2112 byte clusters in use (current/peak)
0/16 mbuf 4096 byte clusters in use (current/peak)
0/16 mbuf 8192 byte clusters in use (current/peak)
185/350 mbuf 9344 byte clusters in use (current/peak)
0/10 mbuf 12288 byte clusters in use (current/peak)
0/48 mbuf 16384 byte clusters in use (current/peak)
0/48 mbuf 65536 byte clusters in use (current/peak)
10344/10360/131072 Kbytes allocated to network (current/peak/max)
0 requests for memory denied
0 requests for memory delayed
0 calls to protocol drain routines
1 defrag mbuf allocation
846 prepend mbuf allocation
0 pullup mbuf allocation
0 pullup memory copy
0 pulldown mbuf allocation
0 pulldown memory copy
dlg@t4-1 ~$ netstat -sp tcp
tcp:
	947225 packets sent
		174820 data packets (68483396 bytes)
		16 data packets (8288 bytes) retransmitted
		0 fast retransmitted packets
		651588 ack-only packets (730194 delayed)
		0 URG only packets
		0 window probe packets
		120833 window update packets
		16 control packets
		0 packets software-checksummed
		0 output TSO large packets chopped in software
		3427 output TSO large packets to device
		38046 output TSO generated packets sent to network
		0 bad TSO packets dropped
	1412337 packets received
		129242 acks (for 68482682 bytes)
		140 duplicate acks
		0 acks for unsent data
		0 acks for old data
		1325149 packets (7122666881 bytes) received in-sequence
		270 completely duplicate packets (487736 bytes)
		137 old duplicate packets
		5 packets with some duplicate data (18824 bytes duplicated)
		56336 out-of-order packets (266824364 bytes)
		0 packets (0 bytes) of data after window
		0 window probes
		1 window update packet
		2 packets received after close
		0 discarded for bad checksums
		0 discarded for bad header offset fields
		0 discarded because packet too short
		0 discarded for missing IPsec protection
		0 discarded due to memory shortage
		0 packets software-checksummed
		0 bad/missing md5 checksums
		0 good md5 checksums
		0 input LRO generated packets glued in software
		697848 input LRO generated packets from device
		4506091 input LRO small packets received from network
		0 bad LRO packets dropped
	6 connection requests
	9 connection accepts
	14 connections established (including accepts)
	14 connections closed (including 2 drops)
	0 connections drained
	0 embryonic connections dropped
	129244 segments updated rtt (of 102306 attempts)
	16 retransmit timeouts
		0 connections dropped by rexmit timeout
	0 persist timeouts
	0 keepalive timeouts
		0 keepalive probes sent
		0 connections dropped by keepalive
	26647 correct ACK header predictions
	1228331 correct data packet header predictions
	19 PCB cache misses
	1 dropped due to no socket
	0 dropped as socket is closing
	0 ECN connections accepted
		0 ECE packets received
		0 CWR packets received
		0 CE packets received
		0 ECT packets sent
		0 ECE packets sent
		0 CWR packets sent
			cwr by fastrecovery: 6
			cwr by timeout: 16
			cwr by ecn: 0
	0 bad connection attempts
	0 SYN packets dropped due to queue or memory full
	9 SYN cache entries added
		0 hash collisions
		9 completed
		0 aborted (no space to build PCB)
		0 timed out
		0 dropped due to overflow
		0 dropped due to bucket overflow
		0 dropped due to RST
		0 dropped due to ICMP unreachable
	0 SYN,ACKs retransmitted
	0 duplicate SYNs received for entries already in the cache
	0 SYNs dropped (no route or no space)
	1 SYN cache seed with new random
	293 hash bucket array size in current SYN cache
	0 entries in current SYN cache, limit is 10255
	0 longest bucket length in current SYN cache, limit is 105
	99991 uses of current SYN cache left
	6 SACK recovery episodes
		0 segment rexmits in SACK recovery episodes
		0 byte rexmits in SACK recovery episodes
	153 SACK options received
	52803 SACK options sent
	0 SACK options dropped
dlg@t4-1 ~$ kstat ix1:::
ix1:0:ix-rxq:0
         packets: 3030955 packets
           bytes: 4531394140 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:1
         packets: 2172116 packets
           bytes: 3238183677 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:2
         packets: 2132 packets
           bytes: 411481 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:3
         packets: 2079 packets
           bytes: 644032 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:4
         packets: 2808 packets
           bytes: 671761 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:5
         packets: 7774 packets
           bytes: 847054 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:6
         packets: 5288 packets
           bytes: 974665 bytes
          qdrops: 0 packets
ix1:0:ix-rxq:7
         packets: 1701 packets
           bytes: 342626 bytes
          qdrops: 0 packets
ix1:0:ix-stats:0
        crc errs: 0 packets
     tx link xon: 0 packets
     rx link xon: 0 packets
    tx link xoff: 0 packets
    rx link xoff: 0 packets
          rx 64B: 56 packets
      rx 65-127B: 77395 packets
     rx 128-255B: 4875 packets
     rx 256-511B: 11043 packets
    rx 512-1023B: 47548 packets
    rx 1024-maxB: 5083936 packets
         tx good: 947230 packets
         rx good: 7794368848 bytes
         tx good: 137786158 bytes
    rx undersize: 0 packets
     rx fragment: 0 packets
     rx oversize: 0 packets
       rx jabber: 0 packets
        rx total: 7795233207 bytes
        rx total: 5230423 packets
        tx total: 947230 packets
         rx good: 5224853 packets
        rx bcast: 26422 packets
        rx mcast: 11551 packets
          tx 64B: 162 packets
      tx 65-127B: 806325 packets
     tx 128-255B: 100555 packets
     tx 256-511B: 324 packets
    tx 512-1023B: 1576 packets
    tx 1024-maxB: 38288 packets
        tx mcast: 2972 packets
        tx bcast: 32 packets
ix1:0:ix-txq:0
         packets: 3065 packets
           bytes: 380582 bytes
ix1:0:ix-txq:1
         packets: 39814 packets
           bytes: 59619838 bytes
ix1:0:ix-txq:2
         packets: 46 packets
           bytes: 5813 bytes
ix1:0:ix-txq:3
         packets: 83 packets
           bytes: 10932 bytes
ix1:0:ix-txq:4
         packets: 20275 packets
           bytes: 2380826 bytes
ix1:0:ix-txq:5
         packets: 883932 packets
           bytes: 71594376 bytes
ix1:0:ix-txq:6
         packets: 2 packets
           bytes: 160 bytes
ix1:0:ix-txq:7
         packets: 13 packets
           bytes: 4207 bytes
ix1:0:rxq:0
         packets: 886976 packets
           bytes: 4377768912 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 439270
        dequeues: 438954
ix1:0:rxq:1
         packets: 507983 packets
           bytes: 3119662441 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 274200
        dequeues: 272644
ix1:0:rxq:2
         packets: 2129 packets
           bytes: 402779 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 2089
        dequeues: 2089
ix1:0:rxq:3
         packets: 2025 packets
           bytes: 632800 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 1917
        dequeues: 1917
ix1:0:rxq:4
         packets: 2808 packets
           bytes: 660529 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 2679
        dequeues: 2679
ix1:0:rxq:5
         packets: 7718 packets
           bytes: 812268 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 7657
        dequeues: 7657
ix1:0:rxq:6
         packets: 5294 packets
           bytes: 954173 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 5119
        dequeues: 5117
ix1:0:rxq:7
         packets: 1701 packets
           bytes: 335822 bytes
          fdrops: 0 packets
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
        enqueues: 1625
        dequeues: 1625
ix1:0:txq:0
         packets: 3066 packets
           bytes: 380334 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:1
         packets: 5200 packets
           bytes: 57176058 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:2
         packets: 46 packets
           bytes: 5629 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:3
         packets: 83 packets
           bytes: 10600 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:4
         packets: 20276 packets
           bytes: 2300024 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:5
         packets: 883932 packets
           bytes: 68058648 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:6
         packets: 2 packets
           bytes: 152 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0
ix1:0:txq:7
         packets: 13 packets
           bytes: 4155 bytes
          qdrops: 0 packets
          errors: 0 packets
            qlen: 0 packets
         maxqlen: 255 packets
         oactive: false
        oactives: 0