Date: Sun, 20 Aug 1995 21:09:10 -0700 From: "Russell L. Carter" <rcarter@geli.com> To: gibbs@freefall.FreeBSD.org, rcarter@geli.com Cc: hackers@freebsd.org Subject: Re: CICA cry for help Message-ID: <199508210409.VAA18033@geli.clusternet>
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Here goes: |From POPmail Sun Aug 20 21:07:46 1995 |Date: Sun, 20 Aug 1995 21:10:59 -0700 |From: Russell Carter <rcarter@best.com> |To: rcarter@geli.com | |>From emo@cica.cica.indiana.edu Sun Aug 20 20:36:46 PDT 1995 |Article: 16936 of comp.os.linux.networking |Path: news1.best.com!news3.net99.net!news.cais.net!ringer.cs.utsa.edu!swrinde!howland.reston.ans.net!vixen.cso.uiuc.edu!usenet.ucs.indiana.edu!cica.cica.indiana.edu!not-for-mail |From: emo@cica.cica.indiana.edu (Eric Ost) |Newsgroups: comp.os.linux.networking,comp.os.linux.setup,comp.os.linux.hardware |Subject: using Linux for heavily-accessed network servers |Date: 19 Aug 1995 20:50:40 -0500 |Organization: Center for Innovative Computer Applications, Indiana University |Lines: 100 |Reply-To: emo@cica.cica.indiana.edu |NNTP-Posting-Host: cica.cica.indiana.edu |Summary: heavily-accessed site w/ random hangs on specific port... suggestions? |Xref: news1.best.com comp.os.linux.networking:16936 comp.os.linux.setup:24546 comp.os.linux.hardware:19443 | |Greetings All, | |I've read testimonials from folks who administer active Internet |sites which are using Linux on a PC and I am hoping that a few |of you will read this note and be able to offer some suggestions. |Has anyone else experienced problems similar to the ones described |below and what corrective actions were taken to resolve them? | |Our site hosts one of the world's most active ftp sites: the CICA ftp software |archive. It also runs httpd and gopher servers as well as handling |a normal load of email and system-related work, e.g. compiles, file edits, |etc. | |Here is the current configuration: | |Hardware |----------------------------------------------------------------------------- |Intel Neptune PCI chipset |Micronics motherboard with P5-90 |128MB RAM |6 GB disk (Seagate 2GB Barracuda, Seagate 4GB Hawk) |Buslogic 946C SCSI-2, PCI controller |SMC EtherPower PCI NIC |----------------------------------------------------------------------------- | |Software |----------------------------------------------------------------------------- |Slackware 2.3 |Linux 1.2.10 |xinetd 2.1.4-linux.3 (master server) |wu-ftpd 2.4 (ftp server) |NCSA httpd 1.4.1 (http server) |gn 2.08 (gopher server) |----------------------------------------------------------------------------- | |We have been experiencing strangeness whereby the system "burps" for a, |sometimes extended, period of time, and connections to port 21 are not |possible -- they just timeout. However, we configured an ftp service |for port 1111 and have discovered that during a "burp" on port 21, |connections to wu-ftpd running on port 1111 are just fine. Telnet (login) |to the machine also works speedily. Random delays have occurred with as low |as 90 and as high as 190 simultaneous connections to port 21; the more |connections, the more likelihood of a delay... | |In all of the above instances, xinetd is playing the role of mediator |between the incoming request and invoking the proper server. | |We have noticed that "netstat" reveals a number of tcp connections in state |FIN_WAIT2. We reduced the default and max timeouts for wu-ftpd to 300 and 600 |seconds, respectively, thinking that perhaps the delays were due to a scarcity |of sockets, with needed resources being tied up in FIN_WAIT2. Reducing |the timeout has reduced the number of processes in FIN_WAIT2, but has not |prevented the random delays. | |The question arises: why do ftp connections to port 1111, telnet/login |to port 23, and smtp via port 25 all connect immediately without delay*? |Connections to these ports depend on allocation of sockets just like the ftp |connection requests to port 21. What are the causative differences here? | |Log file data seems to indicate that wu-ftpd is not being forked by |xinetd on port 21 during these burps while wu-ftpd is being forked speedily |in response to port 1111 requests. Thus, the problem does not appear |to be directly caused by wu-ftpd. Nor does it appear to be caused by |xinetd. If wu-ftpd can be initiated on port 1111 by xinetd, why |can't the same executable be forked to communicate with port 21? | |During these random delays existing connections on port 21 do not seem to |be adversely effected. | |Thinking that lightening the load of xinetd might be in order, we are |now running one instance of xinted on ports 21 and 1111 with another |instance on all the other ports. The delays continue at random times on |port 21 while during these periods connections to port 1111 are speedily |answered. | |At one point the kernel parameter NSOCKETS_LINUX in <net.h> was increased |to 2048, but that did not make any difference either. | |Does anyone have suggestions for further investigation or possibly a |method for resolving this quandary? We have attempted to systematically |narrow the search to focus on the source of the problem. Now we are |wondering if there may be some kind of resource-wait deadlock happening |occasionally somewhere in the system. | |We have been "hanging in there" with Linux for a variety of reasons. |However, we are reaching a point where the problem has become an acute |nuisance and so have been giving serious consideration to switching OS's, |e.g. FreeBSD. | |Any assistance or suggestions folks may lend to resolution of this problem |will be greatly appreciated. The net is a great resource; especially, the |thousands of folks working on developing kernel and application level |code for Linux. | |Any words of wisdom out there? | |Thanks, | |eric | | | | |
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