Merge lp:~mshankar/epics-base/memlock_linux into lp:~epics-core/epics-base/3.15

[Murali Shankar]

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.

[Andrew Johnson (anj)]

Approved, will merge.

review: Approve

=== modified file 'documentation/RELEASE_NOTES.html'
--- documentation/RELEASE_NOTES.html	2014-07-31 17:45:40 +0000
+++ documentation/RELEASE_NOTES.html	2014-08-27 19:21:22 +0000
@@ -15,6 +15,29 @@
 <h2 align="center">Changes between 3.15.0.1 and 3.15.0.2</h2>
 <!-- Insert new items immediately below here ... -->
 
+<h3>On POSIX systems, attempt to lock all memory on startup if running with a 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.  
+  
+In Linux, one can grant a process the ability to run threads with different
+priorities by using a command like <code>ulimit -r unlimited</code>. To use the FIFO
+scheduler, use a command like so - <code>chrt -f 1 softIoc -d test.db</code>
+  
+In Linux, one can grant a process the ability to lock memory by using a command
+like <code>ulimit -l unlimited</code>. Alternatively, these limits can be configured on a per
+user/per group basis by changing /etc/security/limits.conf or its equivalent.
+  
+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)

=== modified file 'src/libCom/osi/os/posix/osdThread.c'
--- src/libCom/osi/os/posix/osdThread.c	2014-05-18 15:24:38 +0000
+++ src/libCom/osi/os/posix/osdThread.c	2014-08-27 19:21:22 +0000
@@ -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 @@
         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 */