pike.git/ src/ gc.c

2014-06-18

2014-06-18 13:36:58 by Henrik Grubbström (Grubba) <grubba@grubba.org>

• 5c248c3cdbacfdc19ded6ac67ef0d2ac570cce1b (162 lines) (+162/-0) ^{[ Show | Annotate ]}
  Branch: 8.0

Pike: Added Pike.identify_cycle().

This is useful to identify reference cycles in Pike data structures,
so that the need for garbage collection can be reduced.

27:   #include "pike_threadlib.h"   #include "gc.h"   #include "main.h" + #include "builtin_functions.h"   #include "block_allocator.h"      #include <math.h>
6051:    pop_n_elems (args);    push_ulongest (return_count ? count_internal : mc_counted_bytes);   } +  + static struct mapping *identify_loop_reverse = NULL; +  + void identify_loop_visit_enter(void *thing, int type, void *extra) + { +  if (type < T_VOID) { +  /* Valid svalue type. */ +  SET_SVAL(*Pike_sp, type, 0, refs, thing); +  add_ref(((struct array *)thing)); +  Pike_sp++; +  } + } +  + void identify_loop_visit_ref(void *dst, int ref_type, +  visit_thing_fn *visit_dst, +  void *extra) + { +  int type = type_from_visit_fn(visit_dst); +  struct mc_marker *ref_to = find_mc_marker(dst); +  if (ref_to) { +  /* Already visited. */ +  return; +  } +  +  if (type != PIKE_T_UNKNOWN) { +  struct svalue s; +  SET_SVAL(s, type, 0, refs, dst); +  low_mapping_insert(identify_loop_reverse, &s, Pike_sp-1, 0); +  } +  +  ref_to = my_make_mc_marker(dst, visit_dst, extra); +  mc_wq_enqueue(ref_to); + } +  + void identify_loop_visit_leave(void *thing, int type, void *extra) + { +  if (type < T_VOID) { +  /* Valid svalue type. */ +  pop_stack(); +  } + } +  + /*! @decl array(mixed) identify_cycle(mixed x) +  *! +  *! Identify reference cycles in Pike datastructures. +  *! +  *! @returns +  *! Returns @expr{UNDEFINED@} if @[x] is not member of a reference cycle. +  *! Otherwise returns an array identifying a cycle with @[x] as the first +  *! element, and where the elements refer to each other in order, and the +  *! last element refers to the first. +  */ + void f_identify_cycle(INT32 args) + { +  struct svalue *s; +  struct mc_marker *m; +  struct svalue *k; +  +  if (args < 1) { +  SIMPLE_TOO_FEW_ARGS_ERROR("identify_loops", 1); +  } +  +  if (args > 1) pop_n_elems(args-1); +  args = 1; +  +  s = Pike_sp - 1; +  +  if (!REFCOUNTED_TYPE(TYPEOF(*s))) { +  SIMPLE_ARG_TYPE_ERROR("identify_loops", 1, +  "array|multiset|mapping|object|program|string|type"); +  } +  if (TYPEOF(*s) == T_FUNCTION) { +  if (SUBTYPEOF(*s) == FUNCTION_BUILTIN) { +  SIMPLE_ARG_TYPE_ERROR("identify_loops", 1, +  "array|multiset|mapping|object|program|string|type"); +  } +  SET_SVAL_TYPE(*s, T_OBJECT); +  } +  +  init_mc_marker_hash(); +  +  if (TYPEOF(pike_cycle_depth_str) == PIKE_T_FREE) { +  SET_SVAL_TYPE(pike_cycle_depth_str, T_STRING); +  MAKE_CONST_STRING (pike_cycle_depth_str.u.string, "pike_cycle_depth"); +  } +  +  assert (mc_work_queue == NULL); +  mc_work_queue = malloc (MC_WQ_START_SIZE * sizeof (mc_work_queue[0])); +  if (!mc_work_queue) { +  exit_mc_marker_hash(); +  SIMPLE_OUT_OF_MEMORY_ERROR ("Pike.count_memory", +  MC_WQ_START_SIZE * sizeof (mc_work_queue[0])); +  } +  mc_work_queue--; +  mc_wq_size = MC_WQ_START_SIZE; +  mc_wq_used = 1; +  mc_lookahead = -1; +  +  assert (!mc_pass); +  assert (visit_enter == NULL); +  assert (visit_ref == NULL); +  assert (visit_leave == NULL); +  +  /* There's a fair chance of there being lots of stuff being referenced, +  * so preallocate a reasonable initial size. +  */ +  identify_loop_reverse = allocate_mapping(1024); +  +  visit_enter = identify_loop_visit_enter; +  visit_ref = identify_loop_visit_ref; +  visit_leave = identify_loop_visit_leave; +  +  /* NB: This initial call will botstrap the wq_queue. */ +  visit_fn_from_type[TYPEOF(*s)](s->u.ptr, VISIT_COMPLEX_ONLY, NULL); +  +  while ((mc_ref_from = mc_wq_dequeue())) { +  if (mc_ref_from->flags & MC_FLAG_INT_VISITED) continue; +  +  mc_ref_from->flags |= MC_FLAG_INT_VISITED; +  mc_ref_from->visit_fn(mc_ref_from->thing, VISIT_COMPLEX_ONLY, NULL); +  } +  +  exit_mc_marker_hash(); +  free (mc_work_queue + 1); +  mc_work_queue = NULL; +  +  visit_enter = NULL; +  visit_ref = NULL; +  visit_leave = NULL; +  + #ifdef PIKE_DEBUG +  if (s != Pike_sp-1) { +  Pike_fatal("Stack error in identify_loops.\n"); +  } + #endif +  +  while ((k = low_mapping_lookup(identify_loop_reverse, Pike_sp-1))) { +  /* NB: Since we entered this loop, we know that there's a +  * reference loop involving s, as s otherwise wouldn't +  * have been in the mapping. +  */ +  push_svalue(k); +  if (k->u.refs == s->u.refs) { +  /* Found! */ +  break; +  } +  } +  +  free_mapping(identify_loop_reverse); +  +  if (!k) { +  push_undefined(); +  } else { +  /* NB: We push s an extra time last above, to simplify the +  * reversing below. +  */ +  f_aggregate(Pike_sp - (s + 1)); +  f_reverse(1); +  } + }