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Return unused parts of the stack to the OS

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* 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.
This commit is contained in:
Andy Wingo 2014-01-31 21:41:36 +01:00
parent 7161ec1133
commit 7dba1c2ff1
3 changed files with 63 additions and 11 deletions
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4
libguile/vm-engine.c
View file

@ -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

59
libguile/vm.c
View file

@ -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);
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,
@ -838,6 +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;
}
@ -884,6 +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)
{
@ -982,6 +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);
@ -1210,6 +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");

7
libguile/vm.h
View file

@ -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 */