Bug #8092: [patch] gc: improve accuracy of objspace_live_num() and allocated/freed counters

• Status: Closed
• Assignee: authorNari (Narihiro Nakamura)
• Target version: -
• ruby -v: ruby 2.1.0dev (2013-03-14 trunk 39748) [x86_64-darwin12.2.1]

[tmm1 (Aman Karmani)]

Test with large rails app:

ruby -e'
require "./config/environment"

stat, count = {}, {}
GC.start
GC.stat(stat)
ObjectSpace.count_objects(count)

printf "%d == %d\n", stat[:heap_live_num], count[:TOTAL]-count[:FREE]

'

Without patch:

632974 == 628506

With patch:

628506 == 628506

diff --git a/gc.c b/gc.c
index bd95073..48f9470 100644
--- a/gc.c
+++ b/gc.c
@@ -1432,10 +1432,8 @@ finalize_list(rb_objspace_t *objspace, RVALUE p)
run_final(objspace, (VALUE)p);
if (!FL_TEST(p, FL_SINGLETON)) { / not freeing page */
add_slot_local_freelist(objspace, p);

•        if (!is_lazy_sweeping(objspace)) {
  

•   objspace->total_freed_object_num++;
  

•   objspace->heap.free_num++;
  

•        }
  

•        objspace->total_freed_object_num++;
  

•        objspace->heap.free_num++;
  

  }
  else {
  struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
  @@ -1939,9 +1937,9 @@ slot_sweep(rb_objspace_t *objspace, struct heaps_slot *sweep_slot)
  else {
  sweep_slot->free_next = NULL;
  }

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

• objspace->total_freed_object_num += freed_num;
  objspace->heap.final_num += final_num;

  if (deferred_final_list && !finalizing) {
  @@ -2965,11 +2963,11 @@ rb_gc_force_recycle(VALUE p)
  rb_objspace_t *objspace = &rb_objspace;
  struct heaps_slot *slot;

• objspace->total_freed_object_num++;
  if (MARKED_IN_BITMAP(GET_HEAP_BITMAP(p), p)) {
  add_slot_local_freelist(objspace, (RVALUE *)p);
  }
  else {

• objspace->total_freed_object_num++;
  objspace->heap.free_num++;
  slot = add_slot_local_freelist(objspace, (RVALUE *)p);
  if (slot->free_next == NULL) {

[authorNari (Narihiro Nakamura)]

• Category set to core
• Assignee set to authorNari (Narihiro Nakamura)

[authorNari (Narihiro Nakamura)]

Thank you for bug report.

But, the following test case is failure.

I think ko1-san is the implementer of GC.stat.
ko1-san, what do you think?

=== start ===
$ git diff test
diff --git a/test/ruby/test_gc.rb b/test/ruby/test_gc.rb
index bed58f3..8cb036a 100644
--- a/test/ruby/test_gc.rb
+++ b/test/ruby/test_gc.rb
@@ -64,6 +64,15 @@ class TestGc < Test::Unit::TestCase
assert_equal(arg, res)
assert_equal(false, res.empty?)
assert_kind_of(Integer, res[:count])
+

• stat, count = {}, {}
• GC.start
• GC.stat(stat)
• ObjectSpace.count_objects(count)
• puts ""
• p stat
• p count
• assert_equal(stat[:heap_live_num], count[:TOTAL]-count[:FREE])
  end

def test_singleton_method

$ % make test-all TESTS='ruby/test_defined.rb ruby/test_integer.rb ruby/test_objectspace.rb ruby/test_sprintf_comb.rb ruby/test_argf.rb ruby/test_fiber.rb ruby/test_gc.rb'
....

Running tests:

[ 91/131] TestGc#test_stat
{:count=>351, :heap_used=>684, :heap_length=>1139, :heap_increment=>399, :heap_live_num=>46061, :heap_free_num=>152639, :heap_final_num=>0, :total_allocated_object=>402509, :total_freed_object=>356448}
{:TOTAL=>198553, :FREE=>152639, :T_OBJECT=>31312, :T_CLASS=>655, :T_MODULE=>56, :T_FLOAT=>10, :T_STRING=>8425, :T_REGEXP=>146, :T_ARRAY=>1966, :T_HASH=>49, :T_STRUCT=>10, :T_BIGNUM=>25, :T_FILE=>10, :T_DATA=>2225, :T_MATCH=>22, :T_COMPLEX=>1, :T_NODE=>934, :T_ICLASS=>68}
= 0.01 s

1. Failure:
   test_stat(TestGc) [/home/nari/source/ruby/ruby-git/test/ruby/test_gc.rb:75]:
   <46061> expected but was
   <45914>.

Finished tests in 6.628281s, 19.7638 tests/s, 657.9383 assertions/s.
131 tests, 4361 assertions, 1 failures, 0 errors, 0 skips

ruby -v: ruby 2.1.0dev (2013-03-14 trunk 38552) [x86_64-linux]
make: *** [yes-test-all] Error 1
=== end ===

[tmm1 (Aman Karmani)]

This test is passing for me on trunk. Before r39811 it is failing.

[ 92/132] TestGc#test_stat
{:count=>357, :heap_used=>421, :heap_length=>811, :heap_increment=>283, :heap_live_num=>14452, :heap_free_num=>156816, :heap_final_num=>0, :total_allocated_object=>389190, :total_freed_object=>374738}
{:TOTAL=>171268, :FREE=>156816, :T_OBJECT=>46, :T_CLASS=>655, :T_MODULE=>56, :T_FLOAT=>10, :T_STRING=>8268, :T_REGEXP=>145, :T_ARRAY=>1947, :T_HASH=>42, :T_STRUCT=>9, :T_BIGNUM=>25, :T_FILE=>3, :T_DATA=>2221, :T_MATCH=>21, :T_COMPLEX=>1, :T_NODE=>935, :T_ICLASS=>68}
Finished tests in 3.297242s, 40.0335 tests/s, 1313.5220 assertions/s.
132 tests, 4331 assertions, 0 failures, 0 errors, 0 skips

ruby -v: ruby 2.1.0dev (2013-03-18 trunk 39811) [x86_64-linux]

[tmm1 (Aman Karmani)]

With this updated patch the test is passing both before and after r39811. Problem was in finalize_list. After r39811 removing heap is less common, so the failure did not appear.

diff --git a/gc.c b/gc.c
index 2afd311..e72b198 100644
--- a/gc.c
+++ b/gc.c
@@ -1431,12 +1431,10 @@ finalize_list(rb_objspace_t *objspace, RVALUE *p)
while (p) {
RVALUE *tmp = p->as.free.next;
run_final(objspace, (VALUE)p);

• objspace->total_freed_object_num++;
  if (!FL_TEST(p, FL_SINGLETON)) { /* not freeing page */
  add_slot_local_freelist(objspace, p);

•        if (!is_lazy_sweeping(objspace)) {
  

•   objspace->total_freed_object_num++;
  

•   objspace->heap.free_num++;
  

•        }
  

•        objspace->heap.free_num++;
  

  }
  else {
  struct heaps_slot *slot = (struct heaps_slot *)(VALUE)RDATA(p)->dmark;
  @@ -1940,9 +1938,9 @@ slot_sweep(rb_objspace_t *objspace, struct heaps_slot *sweep_slot)
  else {
  sweep_slot->free_next = NULL;
  }

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

• objspace->total_freed_object_num += freed_num;
  objspace->heap.final_num += final_num;

  if (deferred_final_list && !finalizing) {
  @@ -2969,11 +2967,11 @@ rb_gc_force_recycle(VALUE p)
  rb_objspace_t *objspace = &rb_objspace;
  struct heaps_slot *slot;

• objspace->total_freed_object_num++;
  if (MARKED_IN_BITMAP(GET_HEAP_BITMAP(p), p)) {
  add_slot_local_freelist(objspace, (RVALUE *)p);
  }
  else {

• objspace->total_freed_object_num++;
  objspace->heap.free_num++;
  slot = add_slot_local_freelist(objspace, (RVALUE *)p);
  if (slot->free_next == NULL) {
  diff --git a/test/ruby/test_gc.rb b/test/ruby/test_gc.rb
  index 90c4787..b1e52fc 100644
  --- a/test/ruby/test_gc.rb
  +++ b/test/ruby/test_gc.rb
  @@ -64,6 +64,12 @@ class TestGc < Test::Unit::TestCase
  assert_equal(arg, res)
  assert_equal(false, res.empty?)
  assert_kind_of(Integer, res[:count])

• stat, count = {}, {}
• GC.start
• GC.stat(stat)
• ObjectSpace.count_objects(count)
• assert_equal(count[:TOTAL]-count[:FREE], stat[:heap_live_num])
  end

def test_singleton_method

[authorNari (Narihiro Nakamura)]

Wow, thanks!! I'll commit it soon.

[authorNari (Narihiro Nakamura)]

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

This issue was solved with changeset r39812.
Aman, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

• gc.c: Improve accuracy of objspace_live_num() and
  allocated/freed counters. patched by tmm1(Aman Gupta).
  [Bug #8092] [ruby-core:53392]