Trac #21805: Use psutil instead of various hacks

The following modules can mostly replaced by simple calls to `psutil`:

* `sage.misc.getusage`
* `sage.misc.memory_info`
* `sage.misc.darwin_utilities`

All usage of these modules is replaced by some simple wrappers around
`psutil`. These wrappers are implemented in `sage.misc.getusage`.

URL: https://trac.sagemath.org/21805
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): Jean-Pierre Flori

Author: Release Manager

src/doc/en/reference/misc/index.rst

@@ -283,7 +283,6 @@ Miscellaneous Inspection and Development Tools
    sage/misc/classgraph
    sage/misc/dev_tools
    sage/misc/function_mangling
-   sage/misc/memory_info
    sage/misc/rest_index_of_methods
 
 Low-Level Utilities

src/module_list.py

@@ -951,12 +951,6 @@ def uname_specific(name, value, alternative):
 
     Extension('*', ['sage/misc/*.pyx']),
 
-    # Only include darwin_utilities on OS_X >= 10.5
-    OptionalExtension('sage.misc.darwin_utilities',
-        sources = ['sage/misc/darwin_memory_usage.c',
-                   'sage/misc/darwin_utilities.pyx'],
-        condition = (UNAME[0] == "Darwin" and not UNAME[2].startswith('8.'))),
-
     ################################
     ##
     ## sage.modular

src/sage/interfaces/gap.py

@@ -257,24 +257,28 @@ def get_gap_memory_pool_size():
 
     EXAMPLES::
 
-        sage: from sage.interfaces.gap import \
-        ...       get_gap_memory_pool_size
+        sage: from sage.interfaces.gap import get_gap_memory_pool_size
         sage: get_gap_memory_pool_size()   # random output
         1534059315
     """
     global gap_memory_pool_size
     if gap_memory_pool_size is not None:
         return gap_memory_pool_size
-    from sage.misc.memory_info import MemoryInfo
-    mem = MemoryInfo()
-    suggested_size = max(mem.available_swap() // 10,
-                         mem.available_ram()  // 50)
+
+    import psutil
+    from sage.misc.getusage import virtual_memory_limit
+    mem = psutil.virtual_memory()
+    swap = psutil.swap_memory()
+    vmax = virtual_memory_limit()
+
+    suggested_size = max(swap.free // 10, mem.available // 50)
     # Don't eat all address space if the user set ulimit -v
-    suggested_size = min(suggested_size, mem.virtual_memory_limit()//10)
+    suggested_size = min(suggested_size, vmax // 10)
     # ~220MB is the minimum for long doctests
     suggested_size = max(suggested_size, 250 * 1024**2)
     return suggested_size
 
+
 def _get_gap_memory_pool_size_MB():
     """
     Return the gap memory pool size suitable for usage on the GAP

src/sage/libs/cypari2/pari_instance.pyx

@@ -510,13 +510,11 @@ cdef class PariInstance(PariInstance_auto):
         # As a simple heuristic, we set the virtual stack to 1/4 of the
         # virtual memory.
 
-        from sage.misc.memory_info import MemoryInfo
-        mem = MemoryInfo()
-
         pari_init_opts(size, maxprime, INIT_DFTm)
-        
-        sizemax = mem.virtual_memory_limit() // 4
 
+        from sage.misc.getusage import virtual_memory_limit
+
+        sizemax = virtual_memory_limit() // 4
         if CYGWIN_VERSION and CYGWIN_VERSION < (2, 5, 2):
             # Cygwin's mmap is broken for large NORESERVE mmaps (>~ 4GB) See
             # http://trac.sagemath.org/ticket/20463 So we set the max stack