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>
 <!-- Insert new items immediately below here ... -->
 
+<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)

src/libCom/osi/os/posix/osdThread.c

@@ -35,6 +35,13 @@
 #include "epicsAssert.h"
 #include "epicsExit.h"
 
+#if defined(linux) 
+#if _POSIX_MEMLOCK > 0
+#include <sys/mman.h>
+#endif
+#endif
+
+
 epicsShareFunc void epicsThreadShowInfo(epicsThreadOSD *pthreadInfo, unsigned int level);
 epicsShareFunc void osdThreadHooksRun(epicsThreadId id);
 epicsShareFunc void osdThreadHooksRunMain(epicsThreadId id);
@@ -344,6 +351,23 @@ static void once(void)
         fprintf(stderr,"sched_get_priority_min failed set to %d\n",
             pcommonAttr->maxPriority);
     }
+
+#if _POSIX_MEMLOCK > 0
+    if(errVerbose)  { 
+        fprintf(stderr, "LRT: min priority: %d max priority %d\n", 
+            pcommonAttr->minPriority, pcommonAttr->maxPriority);
+    }
+    if (pcommonAttr->maxPriority > pcommonAttr->minPriority) {
+        status = mlockall(MCL_CURRENT | MCL_FUTURE);
+        if(status) { 
+            fprintf(stderr, "Unable to lock the virtual address space using mlockall\n");
+        } else { 
+            fprintf(stderr,"Successfully locked memory using mlockAll\n");
+        }
+    }
+#endif
+
+
 #else
     if(errVerbose) fprintf(stderr,"task priorities are not implemented\n");
 #endif /* _POSIX_THREAD_PRIORITY_SCHEDULING */