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Date:      Mon, 30 Jul 2001 10:33:43 -0400
From:      "David E. Cross" <crossd@cs.rpi.edu>
To:        Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>
Cc:        "Matthew E. Martini" <martini@invision.net>, Bill Paul <wpaul@FreeBSD.org>, stable@FreeBSD.org, developers@FreeBSD.org
Subject:   Re: ypserv 
Message-ID:  <200107301433.KAA34464@cs.rpi.edu>
In-Reply-To: Message from Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>  of "Mon, 30 Jul 2001 05:46:49 PDT." <200107301247.f6UCl1L17354@cwsys.cwsent.com> 

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The problem with ypserv is definitely exacerbated with high load (I think
it is a problem in the buffer management code in berkley db)  a home
network simply cannot generate the load to cause this (unless your home
net has about ~40 machines on a switched segment, and the machine
connected to 3 such segments over different interfaces ;)

I also will point out a warning on www.sleepycat.com about using Berkley
DB with new versions on GCC (v1.85/1.86 of Berkley DB specifically).  They
basically say "DON'T". I am in the process of re-writing the Berkley
DB code with some modifications... right now for use in ypserv, but I think
we really should consider replacing the libc stuff with them when complete.

(They are much better in a number of ways... like in that it uses mmap(), 
thereby getting around almost all of the concurrent access problems (no
more lseek()/read()/write() race conditions).  It also pushes the buffer
management problems back onto the VM layer w/o really consuming man memory
for it (since the VM pages are backed by a real file).  I also have 
implimented the R_CURSOR type for sequential access to HASH types, that
alone helps a lot of things :)

--
David Cross                               | email: crossd@cs.rpi.edu 
Lab Director                              | Rm: 308 Lally Hall
Rensselaer Polytechnic Institute,         | Ph: 518.276.2860            
Department of Computer Science            | Fax: 518.276.4033
I speak only for myself.                  | WinNT:Linux::Linux:FreeBSD

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