Enable heap profiling with jemalloc:

The jemalloc library (which must be downloaded and installed separately)
is required to perform heap profiling. Instructions on how to enable heap
profiling with rippled are available in doc/HeapProfiling.md

SConstruct

@@ -230,6 +230,15 @@ def config_base(env):
         env.Prepend(CPPPATH='%s/include' % openssl)
         env.Prepend(LIBPATH=['%s/lib' % openssl])
 
+    # handle command-line arguments
+    profile_jemalloc = ARGUMENTS.get('profile-jemalloc')
+    if profile_jemalloc:
+        env.Append(CPPDEFINES={'PROFILE_JEMALLOC' : profile_jemalloc})
+        env.Append(LIBS=['jemalloc'])
+        env.Append(LIBPATH=[os.path.join(profile_jemalloc, 'lib')])
+        env.Append(CPPPATH=[os.path.join(profile_jemalloc, 'include')])
+        env.Append(LINKFLAGS=['-Wl,-rpath,' + os.path.join(profile_jemalloc, 'lib')])
+
 # Set toolchain and variant specific construction variables
 def config_env(toolchain, variant, env):
     if variant == 'debug':

doc/HeapProfiling.md

@@ -0,0 +1,63 @@
+## Heap profiling of rippled with jemalloc
+
+The jemalloc library provides a good API for doing heap analysis,
+including a mechanism to dump a description of the heap from within the
+running application via a function call. Details on how to perform this
+activity in general, as well as how to acquire the software, are available on
+the jemalloc site:
+[https://github.com/jemalloc/jemalloc/wiki/Use-Case:-Heap-Profiling](https://github.com/jemalloc/jemalloc/wiki/Use-Case:-Heap-Profiling)
+
+jemalloc is acquired separately from rippled, and is not affiliated
+with Ripple Labs. If you compile and install jemalloc from the
+source release with default options, it will install the library and header
+under `/usr/local/lib` and `/usr/local/include`, respectively. Heap
+profiling has been tested with rippled on a Linux platform. It should
+work on platforms on which both rippled and jemalloc are available.
+
+To link rippled with jemalloc, the argument
+`profile-jemalloc=<jemalloc_dir>` is provided after the optional target.
+The `<jemalloc_dir>` argument should be the same as that of the
+`--prefix` parameter passed to the jemalloc configure script when building.
+
+## Examples:
+
+Build rippled with jemalloc library under /usr/local/lib and
+header under /usr/local/include:
+
+    $ scons profile-jemalloc=/usr/local
+
+Build rippled using clang with the jemalloc library under /opt/local/lib
+and header under /opt/local/include:
+
+    $ scons clang profile-jemalloc=/opt/local
+
+----------------------
+
+## Using the jemalloc library from within the code
+
+The `profile-jemalloc` parameter enables a macro definition called
+`PROFILE_JEMALLOC`. Include the jemalloc header file as
+well as the api call(s) that you wish to make within preprocessor
+conditional groups, such as:
+
+In global scope:
+
+    #ifdef PROFILE_JEMALLOC
+    #include <jemalloc/jemalloc.h>
+    #endif
+
+And later, within a function scope:
+
+    #ifdef PROFILE_JEMALLOC
+    mallctl("prof.dump", NULL, NULL, NULL, 0);
+    #endif
+
+Fuller descriptions of how to acquire and use jemalloc's api to do memory
+analysis are available at the [jemalloc
+site.](http://www.canonware.com/jemalloc/)
+
+Linking against the jemalloc library will override
+the system's default `malloc()` and related functions with jemalloc's
+implementation. This is the case even if the code is not instrumented
+to use jemalloc's specific API.
+