[E1000-devel] the exact meaning of "packet buffer overrun"

[fuzhengli <fu...@ar...>]

Hi, Developers:

I'm testing a litter modified ixgbe driver, version 2.3.10, for FreeBSD. 
When I run the test for a while, I found the Rx stall, the detail is:
1 the NIC type is 82599, chipset id is 0x10fb8086.
2 the Rx tail and head register never change, and the rx queues are 
empty, see detail of the  the output of "sysctl dev.ix"
3 ther interrupt still be generated. So I use a variable ixgbe_reg_eicr 
to store the EICR's value in interrupt handler, and find
  the EICR's value is 0x20000(packet buffer overrun), see detail of the 
"kgdb output".
4 the rx rings's rx_base and rx_buffers is correct, see detail of the 
"kgdb output"

So I check the 82599 datasheet for the 0x20000, it says that:
Filed:        Rx Miss
Bits:         17
Init value:  0b
Desc:      Missed packet interrupt is activated for each received packet 
that overflows the Rx packet buffer (overrun). Note that the packet is 
dropped and also increments the associated RXMPC[n] counter.

But I'm not completely understand the "overflows the Rx packet buffer", 
my question is
Does it means NIC got a packet that its size is larger than 1514( the 
length value in the descripter)? or something else ?

Appreciate anyone's reply.

================================
FB# sysctl dev.ix.1 | grep rx
dev.ix.1.rx_processing_limit: 1024
dev.ix.1.queue0.rxd_head: 1191
dev.ix.1.queue0.rxd_tail: 1191
dev.ix.1.queue1.rxd_head: 3560
dev.ix.1.queue1.rxd_tail: 3559
dev.ix.1.queue2.rxd_head: 348
dev.ix.1.queue2.rxd_tail: 347
dev.ix.1.queue3.rxd_head: 2948
dev.ix.1.queue3.rxd_tail: 2947
dev.ix.1.queue4.rxd_head: 15
dev.ix.1.queue4.rxd_tail: 14
dev.ix.1.queue5.rxd_head: 2959
dev.ix.1.queue5.rxd_tail: 2958
dev.ix.1.queue6.rxd_head: 3312
dev.ix.1.queue6.rxd_tail: 3311
dev.ix.1.queue7.rxd_head: 1539
dev.ix.1.queue7.rxd_tail: 1538
dev.ix.1.queue8.rxd_head: 1312
dev.ix.1.queue8.rxd_tail: 1311
dev.ix.1.queue9.rxd_head: 1390
dev.ix.1.queue9.rxd_tail: 1389
dev.ix.1.queue10.rxd_head: 2872
dev.ix.1.queue10.rxd_tail: 2871
dev.ix.1.queue11.rxd_head: 1048
dev.ix.1.queue11.rxd_tail: 1047
dev.ix.1.mac_stats.rx_frames_64: 71316
dev.ix.1.mac_stats.rx_frames_65_127: 21691
dev.ix.1.mac_stats.rx_frames_128_255: 13702
dev.ix.1.mac_stats.rx_frames_256_511: 37987
dev.ix.1.mac_stats.rx_frames_512_1023: 87305
dev.ix.1.mac_stats.rx_frames_1024_1522: 8582390

===========================
kgdb) p/x ixgbe_reg_eicr
$25 = 0x20000
(kgdb)
$39 = 0x0
(kgdb)
$40 = 0x20000
(kgdb)
$41 = 0x20000
(kgdb)
$42 = 0x20000

(kgdb) p ((struct ixgbe_adapter*)0xffffff002c789000)->rx_rings[1]
$58 = {
   me = 1,
   rx_base = 0xfffffffe59c8b000,
   mtx_name = "ix1:rx(1)\000\000\000\000\000\000",
   rx_buffers = 0xfffffffb84994000,
   next_to_refresh = 3559,
   next_to_check = 3560,
}

(kgdb) p ((struct 
ixgbe_adapter*)0xffffff002c789000)->rx_rings[1]->rx_base[3560]
{
   read = {
     pkt_addr = 31651817472, (hex 0x75e986800)
   },
   wb = {
     upper = {
       status_error = 0,
       length = 1514,
       vlan = 0
     }
   }
}

(kgdb) p ((struct 
ixgbe_adapter*)0xffffff002c789000)->rx_rings[1]->rx_buffers[3560]
$61 = {
   m_pack = 0xffffff077063b400,
}



-- 
Fu Zhengli
R&D Dept.
Array Networks (Beijing) Inc.
Tel: +86-10-84446688 ext 336
Email: fu...@ar...