docs/66621: Document fix for "kmem_map too small panics"

Stefan Bethke stb at
Thu May 13 21:30:20 UTC 2004

The following reply was made to PR docs/66621; it has been noted by GNATS.

From: Stefan Bethke <stb at>
To: FreeBSD-gnats-submit at
Subject: Re: docs/66621: Document fix for "kmem_map too small panics"
Date: Thu, 13 May 2004 23:22:56 +0200

 Correct syntax for options line.
 Index: book.sgml
 RCS file: /home/ncvs/doc/en_US.ISO8859-1/books/faq/book.sgml,v
 retrieving revision 1.618
 diff -u -C10 -r1.618 book.sgml
 cvs diff: conflicting specifications of output style
 *** book.sgml   11 May 2004 13:29:47 -0000      1.618
 --- book.sgml   13 May 2004 21:22:14 -0000
 *** 3082,3101 ****
 --- 3082,3125 ----
            <question id="asusk7v-boot-failure">
              <para>The boot floppy hangs on a system with an ASUS K7V
                motherboard.  How do I fix this?</para>
              <para>Go into the BIOS setup and disable the <quote>boot 
 +       <qandaentry>
 +         <question id="kmem-map-too-small">
 +           <para>My system has more than 1 GB of RAM, and I'm getting 
 +             with <quote>kmem_map too small</quote> messages. What is
 +             wrong?</para>
 +         </question>
 +         <answer>
 +           <para>Normally, FreeBSD determines a number of kernel 
 +             such as the maximum number of open files that can be 
 +             concurrently, from the amount of memory installed in the
 +             system.  On systems with one gigabyte of RAM or more, this
 +             <quote>auto-sizing</quote> mechanism may choose values 
 that are
 +             too large, leading to poor performance, or even to
 +             panics.</para>
 +           <para>In this particular case, the kernel memory allocation 
 +             is too small for the amount of memory the kernel believes 
 +             should be able to allocate, hence the panic. Compile your 
 +             kernel, and add the <option>VM_KMEM_SIZE_MAX</option> to 
 +             kernel configuration file. Limiting the maximum size to 
 400 MB
 +             (<option>options 
 +         </answer>
 +       </qandaentry>
      <chapter id="troubleshoot">
            <question id="awre">
              <para>What do I do when I have bad blocks on my hard 
 Stefan Bethke <stb at>   Fon +49 170 346 0140

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