TCP Reassembly Issues

[kerbzo]

Hi,

I 'm experiencing a similar issue but I don't know if mine could be
considered normal behaviour: even if net.inet.tcp.reass.curesegments
is set to 1680 and does not icrease, the output of vmstat -z shows a
high tcpreass fail value that I don't remember in previous (8-STABLE)
builds:

ITEM                   SIZE  LIMIT     USED     FREE      REQ FAIL SLEEP
[...]
socket:                 680,  25602,     740,     754, 4345747,   0,   0
unpcb:                  240,  25600,      85,     459,  148595,   0,   0
ipq:                     56,    819,       0,     378,   16126,   0,   0
udp_inpcb:              392,  25600,      24,     376,  222036,   0,   0
udpcb:                   16,  25704,      24,     480,  222036,   0,   0
tcp_inpcb:              392,  25600,     719,    2391, 3958901,   0,   0
tcpcb:                  976,  25600,     625,     707, 3958901,   0,   0
tcptw:                   72,   5150,      93,    2357, 1486035,   0,   0
syncache:               152,  15375,       2,     398, 1587985,   0,   0
hostcache:              136,  15372,    1490,    4922,  119374,   0,   0
tcpreass:                40,   1680,    1680,       0,  108934,4800302,   0
sackhole:                32,      0,       0,     404,  134750,   0,   0
[...]

System is FreeBSD 9.0-PRERELEASE #8 r227705

Bye,
On Thu, Nov 24, 2011 at 8:02 AM, Kris Bauer <kristoph.bauer at gmail.com> wrote:
> Hello,
>
> I am currently experiencing an issue with FreeBSD 9.0-RC2 r227852 where the
> net.inet.tcp.reass.curesegments value is constantly increasing (and not
> descreasing when there is nominal traffic with the box).  It is causing tcp
> slowdowns as described with kern/155407:
>
> Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session (for
> this socket and any other socket waiting for retransmited packets). After
> exhausted net.inet.tcp.reass.maxsegments allocation new entry in tcp_reass
> failed (for this socket and any other socket waiting for retransmited
> packets).
>
> I have increased the reass.maxsegments value to 16384 to temporarily avoid
> the problem, but the cursegments number keeps rising and it seems it will
> occur again.
>
> Is this an issue that anyone else has seen?  I can provide more information
> if need be.
>
> Thanks,
> Kris
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