PEP 454: add a section "Log calls to the memory allocator"

pep-0454.txt

@@ -439,6 +439,36 @@ Statistic
     Difference of total size of memory blocks in bytes (``int``).
 
 
+Rejected Alternatives
+=====================
+
+Log calls to the memory allocator
+---------------------------------
+
+A different approach is to log calls to ``malloc()``, ``realloc()`` and
+``free()`` functions. Calls can be logged into a file or send to another
+computer through the network. Example of a log entry: name of the
+function, size of the memory block, address of the memory block, Python
+traceback where the allocation occurred, timestamp.
+
+Logs cannot be used directly, getting the current status of the memory
+requires to parse previous logs. For example, it is not possible to get
+directly the traceback of a Python object, like
+``get_object_traceback(obj)`` does with traces.
+
+Python uses objects with a very short lifetime and so makes an extensive
+use of memory allocators. It has an allocator optimized for small
+objects (less than 512 bytes) with a short lifetime.  For example, the
+Python test suites calls ``malloc()``, ``realloc()`` or ``free()``
+270,000 times per second in average. If the size of log entry is 32
+bytes, logging produces 8.2 MB per second or 29.0 GB per hour.
+
+The alternative was rejected because it is less efficient and has less
+features. Parsing logs in a different process or a different computer is
+slower than maintaining traces on allocated memory blocks in the same
+process.
+
+
 Prior Work
 ==========