Date: Wed, 9 Mar 2011 12:29:13 GMT From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/155407: Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session Message-ID: <201103091229.p29CTDcb033511@red.freebsd.org> Resent-Message-ID: <201103091230.p29CUBJE094657@freefall.freebsd.org>
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>Number: 155407
>Category: kern
>Synopsis: Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Mar 09 12:30:11 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator: Slawa Olhovchenkov
>Release: 8.2
>Organization:
>Environment:
FreeBSD mail.haustus.ru 8.2-RC3 FreeBSD 8.2-RC3 #0: Sun Jan 30 06:28:31 UTC 2011 root@mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
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).
te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
if (te == NULL) {
TCPSTAT_INC(tcps_rcvmemdrop);
m_freem(m);
*tlenp = 0;
return (0);
}
That is packet can be reduce reassemble queue dropped.
>How-To-Repeat:
Need high bandwidth-delay channel with high, but rare drop.
After lost incoming TCP segment and before got retranmited this segment net.inet.tcp.reass.maxsegments exhausted.
Software emulation:
Tuning by http://fasterdata.es.net/fasterdata/host-tuning/freebsd/
sysctl net.inet.tcp.recvspace=1048576
sysctl net.inet.ip.dummynet.pipe_slot_limit=3000
ipfw pipe 1 config delay 300 queue 3000
ipfw add 100 pipe 1 ip from test_hot to me
fetch http://test_host/big_file
After reach 7MB/s: ipfw pipe 1 config delay 300 queue 3000 plr 0.1
>Fix:
Workaround: set net.inet.tcp.reass.maxsegments in /boot/loader.conf to big value.
>Release-Note:
>Audit-Trail:
>Unformatted:
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