[Guile-commits] GNU Guile branch, master, updated. v2.1.0-623-g7dba1c2

[Andy Wingo]

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- Log -----------------------------------------------------------------
commit 7dba1c2ff139be60ccf7f81debd4bb85a07ab8f6
Author: Andy Wingo <address@hidden>
Date:   Fri Jan 31 21:41:36 2014 +0100

    Return unused parts of the stack to the OS
    
    * libguile/vm.h (struct scm_vm): Reorder fields.  Add "sp_max_since_gc"
      field.
    * libguile/vm-engine.c (ALLOC_FRAME, RESET_FRAME):
    * libguile/vm.c (vm_return_to_continuation)
      (vm_reinstate_partial_continuation, scm_call_n): In places where we
      could increase the stack height, update sp_max_since_gc.
      (vm_expand_stack): Relocate sp_max_since_gc on expansion.
      (scm_bootstrap_vm): Record the page size using gnulib's getpagesize.
      (return_unused_stack_to_os): New routine, run when marking stacks.

commit 7161ec1133d33a4c06261dd6a621026c3d4d1ef5
Author: Andy Wingo <address@hidden>
Date:   Fri Jan 31 20:31:31 2014 +0100

    Micro-optimization to scm_i_vm_mark_stack
    
    * libguile/vm.c (scm_i_vm_mark_stack): Micro-optimize GC_MARK_AND_PUSH
      to cache the plausible heap bounds locally.

-----------------------------------------------------------------------

Summary of changes:
 libguile/vm-engine.c |    4 +++
 libguile/vm.c        |   70 ++++++++++++++++++++++++++++++++++++++++++-------
 libguile/vm.h        |    7 +++--
 3 files changed, 68 insertions(+), 13 deletions(-)

diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 0caad8a..fe0329f 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -196,6 +196,8 @@
   do {                                                              \
     vp->sp = LOCAL_ADDRESS (n - 1);                                 \
     CHECK_OVERFLOW ();                                              \
+    if (vp->sp > vp->sp_max_since_gc)                               \
+      vp->sp_max_since_gc = vp->sp;                                 \
   } while (0)
 
 /* Reset the current frame to hold N locals.  Used when we know that no
@@ -203,6 +205,8 @@
 #define RESET_FRAME(n)                                              \
   do {                                                              \
     vp->sp = LOCAL_ADDRESS (n - 1);                                 \
+    if (vp->sp > vp->sp_max_since_gc)                               \
+      vp->sp_max_since_gc = vp->sp;                                 \
   } while (0)
 
 /* Compute the number of locals in the frame.  At a call, this is equal
diff --git a/libguile/vm.c b/libguile/vm.c
index 43ade82..7f88e46 100644
--- a/libguile/vm.c
+++ b/libguile/vm.c
@@ -28,6 +28,7 @@
 #include <alignof.h>
 #include <string.h>
 #include <stdint.h>
+#include <unistd.h>
 
 #ifdef HAVE_SYS_MMAN_H
 #include <sys/mman.h>
@@ -142,6 +143,8 @@ vm_return_to_continuation (struct scm_vm *vp, SCM cont, 
size_t n, SCM *argv)
         vp->sp++;
         *vp->sp = argv_copy[i];
       }
+    if (vp->sp > vp->sp_max_since_gc)
+      vp->sp_max_since_gc = vp->sp;
     vp->ip = cp->ra;
   }
 }
@@ -288,6 +291,8 @@ vm_abort (struct scm_vm *vp, SCM tag,
   scm_c_abort (vp, tag, nstack + tail_len, argv, current_registers);
 }
 
+static void vm_expand_stack (struct scm_vm *vp) SCM_NOINLINE;
+
 static void
 vm_reinstate_partial_continuation (struct scm_vm *vp, SCM cont,
                                    size_t n, SCM *argv,
@@ -303,17 +308,25 @@ vm_reinstate_partial_continuation (struct scm_vm *vp, SCM 
cont,
   memcpy (argv_copy, argv, n * sizeof(SCM));
 
   cp = SCM_VM_CONT_DATA (cont);
-  base = SCM_FRAME_LOCALS_ADDRESS (vp->fp);
-  reloc = cp->reloc + (base - cp->stack_base);
+
+  while (1)
+    {
+      scm_t_ptrdiff saved_stack_height = vp->sp - vp->stack_base;
+
+      base = SCM_FRAME_LOCALS_ADDRESS (vp->fp);
+      reloc = cp->reloc + (base - cp->stack_base);
+
+      vp->sp = base + cp->stack_size + n + 1;
+      if (vp->sp < vp->stack_limit)
+        break;
+
+      vm_expand_stack (vp);
+      vp->sp = vp->stack_base + saved_stack_height;
+    }
 
 #define RELOC(scm_p)                                           \
   (((SCM *) (scm_p)) + reloc)
 
-  if ((base - vp->stack_base) + cp->stack_size + n + 1 > vp->stack_size)
-    scm_misc_error ("vm-engine",
-                    "not enough space to instate partial continuation",
-                    scm_list_1 (cont));
-
   memcpy (base, cp->stack_base, cp->stack_size * sizeof (SCM));
 
   /* now relocate frame pointers */
@@ -336,6 +349,9 @@ vm_reinstate_partial_continuation (struct scm_vm *vp, SCM 
cont,
       *vp->sp = argv_copy[i];
     }
 
+  if (vp->sp > vp->sp_max_since_gc)
+      vp->sp_max_since_gc = vp->sp;
+
   /* The prompt captured a slice of the dynamic stack.  Here we wind
      those entries onto the current thread's stack.  We also have to
      relocate any prompts that we see along the way.  */
@@ -672,7 +688,6 @@ initialize_default_stack_size (void)
     default_max_stack_size = size;
 }
 
-static void vm_expand_stack (struct scm_vm *vp) SCM_NOINLINE;
 #define VM_NAME vm_regular_engine
 #define VM_USE_HOOKS 0
 #define FUNC_NAME "vm-regular-engine"
@@ -788,6 +803,27 @@ make_vm (void)
 }
 #undef FUNC_NAME
 
+static size_t page_size;
+
+static void
+return_unused_stack_to_os (struct scm_vm *vp)
+{
+#if HAVE_SYS_MMAN_H
+  scm_t_uintptr start = (scm_t_uintptr) vp->sp;
+  scm_t_uintptr end = (scm_t_uintptr) vp->sp_max_since_gc;
+
+  start = ((start - 1U) | (page_size - 1U)) + 1U; /* round up */
+  end = ((end - 1U) | (page_size - 1U)) + 1U; /* round up */
+
+  /* Return these pages to the OS.  The next time they are paged in,
+     they will be zeroed.  */
+  if (start < end)
+    madvise ((void *) start, end - start, MADV_DONTNEED);
+
+  vp->sp_max_since_gc = vp->sp;
+#endif
+}
+
 /* Mark the VM stack region between its base and its current top.  */
 struct GC_ms_entry *
 scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry *mark_stack_ptr,
@@ -800,13 +836,16 @@ scm_i_vm_mark_stack (struct scm_vm *vp, struct 
GC_ms_entry *mark_stack_ptr,
      hooks, and providing dead slot maps for all points in a program
      would take a prohibitive amount of space.  */
   const scm_t_uint8 *dead_slots = NULL;
+  scm_t_uintptr upper = (scm_t_uintptr) GC_greatest_plausible_heap_addr;
+  scm_t_uintptr lower = (scm_t_uintptr) GC_least_plausible_heap_addr;
 
   for (fp = vp->fp, sp = vp->sp; fp; fp = SCM_FRAME_DYNAMIC_LINK (fp))
     {
       for (; sp >= &SCM_FRAME_LOCAL (fp, 0); sp--)
         {
           SCM elt = *sp;
-          if (SCM_NIMP (elt))
+          if (SCM_NIMP (elt)
+              && SCM_UNPACK (elt) >= lower && SCM_UNPACK (elt) <= upper)
             {
               if (dead_slots)
                 {
@@ -820,7 +859,7 @@ scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry 
*mark_stack_ptr,
                     }
                 }
 
-              mark_stack_ptr = GC_MARK_AND_PUSH ((GC_word *) elt,
+              mark_stack_ptr = GC_mark_and_push ((void *) elt,
                                                  mark_stack_ptr,
                                                  mark_stack_limit,
                                                  NULL);
@@ -835,6 +874,8 @@ scm_i_vm_mark_stack (struct scm_vm *vp, struct GC_ms_entry 
*mark_stack_ptr,
         scm_find_dead_slot_map_unlocked (SCM_FRAME_RETURN_ADDRESS (fp));
     }
 
+  return_unused_stack_to_os (vp);
+
   return mark_stack_ptr;
 }
 
@@ -881,6 +922,7 @@ vm_expand_stack (struct scm_vm *vp)
           SCM *fp;
           vp->fp += reloc;
           vp->sp += reloc;
+          vp->sp_max_since_gc += reloc;
           fp = vp->fp;
           while (fp)
             {
@@ -979,6 +1021,9 @@ scm_call_n (SCM proc, SCM *argv, size_t nargs)
   vp->fp = &base[5];
   vp->sp = &SCM_FRAME_LOCAL (vp->fp, nargs);
 
+  if (vp->sp > vp->sp_max_since_gc)
+    vp->sp_max_since_gc = vp->sp;
+
   {
     int resume = SCM_I_SETJMP (registers);
       
@@ -1207,6 +1252,11 @@ scm_bootstrap_vm (void)
                             (scm_t_extension_init_func)scm_init_vm_builtins,
                             NULL);
 
+  page_size = getpagesize ();
+  /* page_size should be a power of two.  */
+  if (page_size & (page_size - 1))
+    abort ();
+
   initialize_default_stack_size ();
 
   sym_vm_run = scm_from_latin1_symbol ("vm-run");
diff --git a/libguile/vm.h b/libguile/vm.h
index 6a25732..9edced1 100644
--- a/libguile/vm.h
+++ b/libguile/vm.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, 
Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013, 2014 Free Software 
Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -39,10 +39,11 @@ struct scm_vm {
   scm_t_uint32 *ip;            /* instruction pointer */
   SCM *sp;                     /* stack pointer */
   SCM *fp;                     /* frame pointer */
-  size_t stack_size;           /* stack size */
-  SCM *stack_base;             /* stack base address */
   SCM *stack_limit;            /* stack limit address */
   int trace_level;              /* traces enabled if trace_level > 0 */
+  SCM *sp_max_since_gc;         /* highest sp since last gc */
+  size_t stack_size;           /* stack size */
+  SCM *stack_base;             /* stack base address */
   size_t max_stack_size;
   SCM hooks[SCM_VM_NUM_HOOKS]; /* hooks */
   int engine;                   /* which vm engine we're using */


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