Merged Murali's memlock_all branch.

documentation/RELEASE_NOTES.html

@@ -15,6 +15,29 @@ EPICS Base 3.15.0.x releases are not intended for use in production systems.</p>
 <h2 align="center">Changes between 3.15.0.1 and 3.15.0.2</h2>
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+<h3>On POSIX, attempt to lock all memory when running with FIFO scheduler</h3>
+
+<p>On POSIX systems, an IOC application's ability to meet timing deadlines is often
+dependent on its ability to lock part or all of the process's virtual address space
+into RAM, preventing that memory from being paged to the swap area. This change will
+attempt to lock the process's virtual address space into RAM if the process has the
+ability to run threads with different priorities. If unsuccessful, it prints an
+message to stderr and continues.</p>
+ 
+<p>On Linux, one can grant a process the ability to run threads with different
+priorities by using the command <code>ulimit -r unlimited</code>. To use the FIFO
+scheduler for an IOC, use a command like this:</p>
+
+<blockquote><pre>chrt -f 1 softIoc -d test.db</pre></blockquote>
+ 
+<p>On Linux, one can grant a process the ability to lock memory using the command
+<code>ulimit -l unlimited</code>. These limits can also be configured on a per
+user/per group basis by changing /etc/security/limits.conf or its equivalent.</p>
+ 
+<p>In Linux, a child process created via fork inherits its parent's resource
+limits. Thus, it is probably a good idea to start the caRepeater before
+starting the IOC.</p>
+
 <h3>Implement EPICS_CAS_INTF_ADDR_LIST in rsrv</h3>
 
 <p>The IOC server can now bind to a single IP address (and optional port number)