Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!bloom-beacon!adam.pika.mit.edu!scs From: scs@adam.pika.mit.edu (Steve Summit) Newsgroups: comp.bugs.4bsd Subject: TIME_WAIT sockets clog system Keywords: ftp mbufs time_wait drain Message-ID: <12417@bloom-beacon.MIT.EDU> Date: 4 Jul 89 01:52:55 GMT References: Sender: daemon@bloom-beacon.MIT.EDU Reply-To: scs@adam.pika.mit.edu (Steve Summit) Distribution: na Lines: 37 There is an interesting discussion going on in comp.bugs.2bsd about an out-of-mbufs problem caused by an mget in ftp. The problem obviously occurs primarily on a pdp11 with its limited memory, but the 2.10bsd code is taken directly from the VAX version, and I have noticed the same problem (and indeed the original submittor acknowledges the possibility in the excerpt from his posting I've reproduced below) when doing an mput (as I recall) on an overloaded MicroVAX being used as a file server. In article sms@wlv.imsd.contel.com (Steven M. Schultz(Y)) writes: G>Subject: TIME_WAIT sockets clog system (part 2) O>Index: sys/sys/uipc_mbuf.c 2.10BSD O> D>Description: > Sockets in a TIME_WAIT state can constipate the networking O> buffer memory when generated in rapid succession by, for L> example, an "mget" in an ftp session. If more than a dozen D> or so small files are transferred in rapid succession over > an ethernet, all the mbufs in the system will be taken up I> by sockets in a TIME_WAIT state (from the socket opened for N> each data transfer). E> W>Repeat-By: S> ftp in to a 2.10.1BSD system, do an "mget *" in a largish > directory. note that the transfer will hang/develope problems > after about a dozen to twenty files. the 2.10.1BSD system > has run out of mbufs and will recover in a minute or so (hopefully). > It should be noted that even a Vax could be run out of mbufs > if the directory were large enough and network memory was full > due to other causes. There is some debate about the efficacy of the proposed fix, which involves fleshing out the (previously stubbed) tcp_drain routine. Steve Summit scs@adam.pika.mit.edu