cvs commit: httpd-2.0/docs/manual/misc perf-tuning.html

[br...@apache.org]

brianp      02/05/24 23:58:39

  Modified:    docs/manual/misc perf-tuning.html
  Log:
  Added EnableMMAP to performance tuning guide
  
  Revision  Changes    Path
  1.31      +31 -0     httpd-2.0/docs/manual/misc/perf-tuning.html
  
  Index: perf-tuning.html
  ===================================================================
  RCS file: /home/cvs/httpd-2.0/docs/manual/misc/perf-tuning.html,v
  retrieving revision 1.30
  retrieving revision 1.31
  diff -u -r1.30 -r1.31
  --- perf-tuning.html	31 Dec 2001 02:29:12 -0000	1.30
  +++ perf-tuning.html	25 May 2002 06:58:39 -0000	1.31
  @@ -69,6 +69,8 @@
            <a
           href="../mod/core.html#hostnamelookups">HostnameLookups</a><br />
            <a
  +        href="../mod/core.html#enablemmap">EnableMMAP</a><br />
  +         <a
           href="../mod/core.html#keepalivetimeout">KeepAliveTimeout</a><br />
            <a
           href="../mod/prefork.html#maxspareservers">MaxSpareServers</a><br />
  @@ -280,6 +282,35 @@
       <code>MultiViews</code>, as the necessary information can be
       determined by reading this single file, rather than having to
       scan the directory for files.</p>
  +
  +    <h4>Memory-mapping</h4>
  +
  +    <p>In situations where Apache 2.0 needs to look at the contents
  +    of a file being delivered--for example, when doing server-side-include
  +    processing--it normally memory-maps the file if the OS supports
  +    some form of mmap(2).
  +    </p>
  +
  +    <p>On some platforms, this memory-mapping improves performance.
  +    However, there are cases where memory-mapping can hurt the performance
  +    or even the stability of the httpd:</p>
  +
  +    <ul>
  +      <li>On some operating systems, mmap does not scale as well as
  +      read(2) when the number of CPUs increases.  On multiprocessor
  +      Solaris servers, for example, Apache 2.0 sometimes delivers
  +      server-parsed files faster when mmap is disabled.</li>
  +
  +      <li>If you memory-map a file located on an NFS-mounted filesystem
  +      and a process on another NFS client machine deletes or truncates
  +      the file, your process may get a bus error the next time it tries
  +      to access the mapped file content.</li>
  +    </ul>
  +
  +    <p>For installations where either of these factors applies, you
  +    should use <code>EnableMMAP off</code> to disable the memory-mapping
  +    of delivered files.  (Note: This directive can be overridden on
  +    a per-directory basis.)</p>
   
       <h4>Process Creation</h4>