Bug #8122: [patch] gc: GC.stat improvements and related cleanup

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: 2.1.0
• ruby -v: ruby 2.1.0dev (2013-03-19 trunk 39816) [x86_64-darwin12.2.1]

[tmm1 (Aman Karmani)]

I propose 4 related patches below. The end result is more information from GC.stat about mark and sweep activity.

1. Rename heap.free_num to heap.swept_num
   This is a purely cosmetic change, to make the purpose of the variable more clear and avoid problems due to misuse later (like we saw in r39811)
   I considered some other names: heap.freelisted_num, heap.reused_num

2. Add heap.sweep_num
   We already calculate heap.marked_num during mark. This is inverse of marked_num calculated at the end of mark cycle.
   Using this you can monitor progress of sweep cycle: (100% * heap.swept_num / heap.sweep_num)
   I considered also: heap.sweeping_num

3. Remove rest_sweep() from GC.stat
   Currently sweep is a side-effect of GC.stat. It makes GC.stat difficult to use for statistics, because it is not constant time operation.
   Also, after rest_sweep(), heap.swept_num == heap.sweep_num, so GC.stat cannot be used to track progress of sweep cycle.

4. Expose new mark/sweep counters via GC.stat

Author: Aman Gupta [e-mail]
Date: Mon Mar 18 18:11:27 2013 -0700

rename heap.free_num to heap.swept_num

diff --git a/gc.c b/gc.c
index 635e3ec..f654e19 100644
--- a/gc.c
+++ b/gc.c
@@ -229,7 +229,7 @@ typedef struct rb_objspace {
RVALUE *range[2];
struct heaps_header *freed;
size_t marked_num;

• size_t free_num;

• size_t swept_num;
  size_t free_min;
  size_t final_num;
  size_t do_heap_free;
  @@ -1434,7 +1434,7 @@ finalize_list(rb_objspace_t *objspace, RVALUE p)
  objspace->total_freed_object_num++;
  if (!FL_TEST(p, FL_SINGLETON)) { / not freeing page */
  add_slot_local_freelist(objspace, p);

•   objspace->heap.free_num++;
  

•   objspace->heap.swept_num++;
  

  }
  else {
  struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
  @@ -1921,7 +1921,7 @@ slot_sweep(rb_objspace_t *objspace, struct heaps_slot *sweep_slot)
  }
  gc_clear_slot_bits(sweep_slot);
  if (final_num + freed_num + empty_num == sweep_slot->header->limit &&

•    objspace->heap.free_num > objspace->heap.do_heap_free) {
  

•    objspace->heap.swept_num > objspace->heap.do_heap_free) {
     RVALUE *pp;
  
     for (pp = deferred_final_list; pp != final; pp = pp->as.free.next) {
  

@@ -1938,7 +1938,7 @@ slot_sweep(rb_objspace_t *objspace, struct heaps_slot *sweep_slot)
else {
sweep_slot->free_next = NULL;
}

• objspace->heap.free_num += freed_num + empty_num;

• objspace->heap.swept_num += freed_num + empty_num;
  }
  objspace->total_freed_object_num += freed_num;
  objspace->heap.final_num += final_num;
  @@ -1977,7 +1977,7 @@ before_gc_sweep(rb_objspace_t *objspace)
  objspace->heap.do_heap_free = initial_free_min;
  }
  objspace->heap.sweep_slots = heaps;

• objspace->heap.free_num = 0;

• objspace->heap.swept_num = 0;
  objspace->heap.free_slots = NULL;

  /* sweep unlinked method entries */
  @@ -1992,7 +1992,7 @@ after_gc_sweep(rb_objspace_t *objspace)
  size_t inc;

  gc_prof_set_malloc_info(objspace);

• if (objspace->heap.free_num < objspace->heap.free_min) {

• if (objspace->heap.swept_num < objspace->heap.free_min) {
  set_heaps_increment(objspace);
  heaps_increment(objspace);
  }
  @@ -2972,7 +2972,7 @@ rb_gc_force_recycle(VALUE p)
  add_slot_local_freelist(objspace, (RVALUE *)p);
  }
  else {

• objspace->heap.free_num++;

• objspace->heap.swept_num++;
  slot = add_slot_local_freelist(objspace, (RVALUE *)p);
  if (slot->free_next == NULL) {
  link_free_heap_slot(objspace, slot);
  @@ -3205,7 +3205,7 @@ gc_stat(int argc, VALUE *argv, VALUE self)
  rb_hash_aset(hash, sym_heap_length, SIZET2NUM(objspace->heap.length));
  rb_hash_aset(hash, sym_heap_increment, SIZET2NUM(objspace->heap.increment));
  rb_hash_aset(hash, sym_heap_live_num, SIZET2NUM(objspace_live_num(objspace)));

• rb_hash_aset(hash, sym_heap_free_num, SIZET2NUM(objspace->heap.free_num));

• rb_hash_aset(hash, sym_heap_free_num, SIZET2NUM(objspace->heap.swept_num));
  rb_hash_aset(hash, sym_heap_final_num, SIZET2NUM(objspace->heap.final_num));
  rb_hash_aset(hash, sym_total_allocated_object, SIZET2NUM(objspace->total_allocated_object_num));
  rb_hash_aset(hash, sym_total_freed_object, SIZET2NUM(objspace->total_freed_object_num));

Author: Aman Gupta [e-mail]
Date: Mon Mar 18 18:32:58 2013 -0700

add sweep_num

diff --git a/gc.c b/gc.c
index b911d04..c49f1dd 100644
--- a/gc.c
+++ b/gc.c
@@ -229,6 +229,7 @@ typedef struct rb_objspace {
RVALUE *range[2];
struct heaps_header *freed;
size_t marked_num;

• size_t sweep_num;
  size_t swept_num;
  size_t free_min;
  size_t final_num;
  @@ -2957,6 +2958,7 @@ gc_marks(rb_objspace_t *objspace)
  gc_prof_mark_timer_stop(objspace);

  objspace->mark_func_data = prev_mark_func_data;

• objspace->heap.sweep_num = (heaps_used * HEAP_OBJ_LIMIT) - objspace->heap.marked_num;
  }

/* GC */

Author: Aman Gupta [e-mail]
Date: Mon Mar 18 18:14:10 2013 -0700

remove rest_sweep side-effect from GC.stat

diff --git a/gc.c b/gc.c
index f654e19..b911d04 100644
--- a/gc.c
+++ b/gc.c
@@ -3197,8 +3197,6 @@ gc_stat(int argc, VALUE *argv, VALUE self)
hash = rb_hash_new();
}

• rest_sweep(objspace);
• rb_hash_aset(hash, sym_count, SIZET2NUM(objspace->count));
  /* implementation dependent counters */
  rb_hash_aset(hash, sym_heap_used, SIZET2NUM(objspace->heap.used));

Author: Aman Gupta [e-mail]
Date: Mon Mar 18 18:59:50 2013 -0700

add more stats to GC.stat

diff --git a/gc.c b/gc.c
index c49f1dd..8f458db 100644
--- a/gc.c
+++ b/gc.c
@@ -3174,18 +3174,28 @@ gc_stat(int argc, VALUE *argv, VALUE self)
{
rb_objspace_t *objspace = &rb_objspace;
VALUE hash;

• size_t total_num, live_num;
  static VALUE sym_count;
  static VALUE sym_heap_used, sym_heap_length, sym_heap_increment;

• static VALUE sym_heap_live_num, sym_heap_free_num, sym_heap_final_num;

• static VALUE sym_heap_obj_limit, sym_heap_total_num;
• static VALUE sym_heap_live_num, sym_heap_empty_num, sym_heap_final_num;
• static VALUE sym_heap_marked_num, sym_heap_sweep_num, sym_heap_swept_num;
• static VALUE sym_is_lazy_sweeping;
  static VALUE sym_total_allocated_object, sym_total_freed_object;
  if (sym_count == 0) {
  sym_count = ID2SYM(rb_intern_const("count"));
  sym_heap_used = ID2SYM(rb_intern_const("heap_used"));
  sym_heap_length = ID2SYM(rb_intern_const("heap_length"));
  sym_heap_increment = ID2SYM(rb_intern_const("heap_increment"));
• sym_heap_obj_limit = ID2SYM(rb_intern_const("heap_obj_limit"));
• sym_heap_total_num = ID2SYM(rb_intern_const("heap_total_num"));
  sym_heap_live_num = ID2SYM(rb_intern_const("heap_live_num"));

• sym_heap_free_num = ID2SYM(rb_intern_const("heap_free_num"));

• sym_heap_empty_num = ID2SYM(rb_intern_const("heap_empty_num"));
  sym_heap_final_num = ID2SYM(rb_intern_const("heap_final_num"));

• sym_heap_marked_num = ID2SYM(rb_intern_const("heap_marked_num"));

• sym_heap_sweep_num = ID2SYM(rb_intern_const("heap_sweep_num"));

• sym_heap_swept_num = ID2SYM(rb_intern_const("heap_swept_num"));

• sym_is_lazy_sweeping = ID2SYM(rb_intern_const("is_lazy_sweeping"));
  sym_total_allocated_object = ID2SYM(rb_intern_const("total_allocated_object"));
  sym_total_freed_object = ID2SYM(rb_intern_const("total_freed_object"));
  }
  @@ -3201,12 +3211,21 @@ gc_stat(int argc, VALUE *argv, VALUE self)

  rb_hash_aset(hash, sym_count, SIZET2NUM(objspace->count));
  /* implementation dependent counters */

• total_num = heaps_used * HEAP_OBJ_LIMIT;

• live_num = objspace_live_num(objspace);

• rb_hash_aset(hash, sym_heap_used, SIZET2NUM(objspace->heap.used));
  rb_hash_aset(hash, sym_heap_length, SIZET2NUM(objspace->heap.length));
  rb_hash_aset(hash, sym_heap_increment, SIZET2NUM(objspace->heap.increment));

• rb_hash_aset(hash, sym_heap_live_num, SIZET2NUM(objspace_live_num(objspace)));
• rb_hash_aset(hash, sym_heap_free_num, SIZET2NUM(objspace->heap.swept_num));

• rb_hash_aset(hash, sym_heap_obj_limit, SIZET2NUM(HEAP_OBJ_LIMIT));
• rb_hash_aset(hash, sym_heap_total_num, SIZET2NUM(total_num));
• rb_hash_aset(hash, sym_heap_live_num, SIZET2NUM(live_num));
• rb_hash_aset(hash, sym_heap_empty_num, SIZET2NUM(total_num - live_num));
  rb_hash_aset(hash, sym_heap_final_num, SIZET2NUM(objspace->heap.final_num));
• rb_hash_aset(hash, sym_is_lazy_sweeping, is_lazy_sweeping(objspace) ? Qtrue : Qfalse);
• rb_hash_aset(hash, sym_heap_marked_num, SIZET2NUM(objspace->heap.marked_num));
• rb_hash_aset(hash, sym_heap_swept_num, SIZET2NUM(objspace->heap.swept_num));
• rb_hash_aset(hash, sym_heap_sweep_num, SIZET2NUM(objspace->heap.sweep_num));
  rb_hash_aset(hash, sym_total_allocated_object, SIZET2NUM(objspace->total_allocated_object_num));
  rb_hash_aset(hash, sym_total_freed_object, SIZET2NUM(objspace->total_freed_object_num));

[authorNari (Narihiro Nakamura)]

• Assignee changed from authorNari (Narihiro Nakamura) to ko1 (Koichi Sasada)

ko1-san, what do you think?

[ko1 (Koichi Sasada)]

(2013/03/19 11:58), authorNari (Narihiro Nakamura) wrote:

ko1-san, what do you think?

(1) Performance

One concern is making it fat seems slow it down.

(2) Usage

How to use new statistics?

--
// SASADA Koichi at atdot dot net

[ko1 (Koichi Sasada)]

• Target version set to 2.1.0

[tmm1 (Aman Karmani)]

• Status changed from Open to Closed
• % Done changed from 0 to 100