If the previous instruction is not a leaf instruction, then the PC was
incremented before the instruction was ran (meaning the currently
executing instruction is actually the previous instruction), so we
should not increment the PC otherwise we will calculate the source
line for the next instruction.
This bug can be reproduced in the following script:
```
require "objspace"
ObjectSpace.trace_object_allocations_start
a =
1.0 / 0.0
p [ObjectSpace.allocation_sourceline(a), ObjectSpace.allocation_sourcefile(a)]
```
Which outputs: [4, "test.rb"]
This is incorrect because the object was allocated on line 10 and not
line 4. The behaviour is correct when we use a leaf instruction (e.g.
if we replaced `1.0 / 0.0` with `"hello"`), then the output is:
[10, "test.rb"].
[Bug #19456]
We shouldn't run gc_verify_internal_consistency after every GC step
when RGENGC_CHECK_MODE >= 2, only when GC has finished. Running it
on every GC step makes it too slow.
There is a `time` key in GC.stat that gives us the total time spent in
GC. However, we don't know what proportion of the time is spent between
marking and sweeping. This makes it difficult to tune the GC as we're
not sure where to focus our efforts on.
This PR adds keys `marking_time` and `sweeping_time` to GC.stat for the
time spent marking and sweeping, in milliseconds.
[Feature #19437]
This macro is broken when set to anything other than 0. And has had a
comment saying that it's broken for 3 years.
This commit deletes it and the associated logging code. It's clearly
not being used.
Co-Authored-By: Peter Zhu <peter@peterzhu.ca>
Given that signleton classes don't have an allocator,
we can re-use these bytes to store the attached object
in `rb_classext_struct` without making it larger.
The old RUBY_GC_HEAP_INIT_SLOTS isn't really usable anymore as
it initalize all the pools by the same factor, but it's unlikely
that pools will need similar sizes.
In production our 40B pool is 5 to 6 times bigger than our 80B pool.
It's not uncommon for simple binding to wrap structs without
any Ruby object references. Hence with no `mark` function.
Might as well mark them as protected by a write barrier.
There's a memory leak in ObjectSpace::WeakMap due to not freeing
the `struct weakmap`. It can be seen in the following script:
```
100.times do
10000.times do
ObjectSpace::WeakMap.new
end
# Output the Resident Set Size (memory usage, in KB) of the current Ruby process
puts `ps -o rss= -p #{$$}`
end
```
Instance variables held in gen_ivtbl are marked with rb_gc_mark. It
prevents the referenced objects from moving, which is bad for copying
garbage collectors.
This commit allows those instance variables to be updated during
gc_update_object_references.
This commit adds rb_gc_mark_and_move which takes a pointer to an object
and marks it during marking phase and updates references during compaction.
This allows for marking and reference updating to be combined into a
single function, which reduces code duplication and prevents bugs if
marking and reference updating goes out of sync.
This commit also implements rb_gc_mark_and_move on iseq as an example.
This commit moves the classpath (and tmp_classpath) from instance
variables to the rb_classext_t. This improves performance as we no
longer need to set an instance variable when assigning a classpath to
a class.
I benchmarked with the following script:
```ruby
name = :MyClass
puts(Benchmark.measure do
10_000_000.times do |i|
Object.const_set(name, Class.new)
Object.send(:remove_const, name)
end
end)
```
Before this patch:
```
5.440119 0.025264 5.465383 ( 5.467105)
```
After this patch:
```
4.889646 0.028325 4.917971 ( 4.942678)
```
The reference updating code for strings is not re-embedding strings
because the code is incorrectly wrapped inside of a
`if (STR_SHARED_P(obj))` clause. Shared strings can't be re-embedded
so this ends up being a no-op. This means that strings can be moved to a
large size pool during compaction, but won't be re-embedded, which would
waste the space.
There is an integer underflow when the environment variable
RUBY_GC_HEAP_INIT_SLOTS is less than the number of slots currently
in the Ruby heap.
[Bug #19284]
If a size pooll is small, then `min_free_slots < heap_init_slots` is true.
This means that min_free_slots will be set to heap_init_slots. This
causes `swept_slots < min_free_slots` to be true in a later if statement.
The if statement could trigger a major GC which could cause major GC
thrashing.
gc_compact_move incorrectly returns false when destination heap is full
after sweeping. It returns false even if destination heap is different
than source heap (returning false means that the source heap has
finished compacting). This causes the source page to get locked, which
causes a read barrier fire when we try to compact the source heap again.
We eagerly set the new shape of an object when moving an object during
compaction. This new shape may have a different capacity than the
current original shape capacity. This means that we cannot copy from the
original buffer using size of the new capacity. Instead, we should use
the ivar count (which is less than or equal to both the new and original
capacities).
Co-Authored-By: Matt Valentine-House <matt@eightbitraptor.com>
Allocating memory (xmalloc and xrealloc) during GC could cause GC to
trigger, which would crash with `[BUG] during_gc != 0`. This is an
intermittent bug which could be hard to debug.
This commit changes it so that any memory allocation during GC will
emit a warning. When debug flags are enabled it will also cause a crash.
When moving Objects between size pools we have to assign a new shape.
This happened during updating references - we tried to create a new shape
tree that mirrored the existing tree, but based on the root shape of the
new size pool.
This causes allocations to happen if the new tree doesn't already exist,
potentially triggering a GC, during GC.
This commit changes object movement to look for a pre-existing new tree
during object movement, and if that tree does not exist, we don't move
the object to the new pool.
This allows us to remove the shape allocation from update references.
Co-Authored-By: Peter Zhu <peter@peterzhu.ca>
When an object becomes "too complex" (in other words it has too many
variations in the shape tree), we transition it to use a "too complex"
shape and use a hash for storing instance variables.
Without this patch, there were rare cases where shape tree growth could
"explode" and cause performance degradation on what would otherwise have
been cached fast paths.
This patch puts a limit on shape tree growth, and gracefully degrades in
the rare case where there could be a factorial growth in the shape tree.
For example:
```ruby
class NG; end
HUGE_NUMBER.times do
NG.new.instance_variable_set(:"@unique_ivar_#{_1}", 1)
end
```
We consider objects to be "too complex" when the object's class has more
than SHAPE_MAX_VARIATIONS (currently 8) leaf nodes in the shape tree and
the object introduces a new variation (a new leaf node) associated with
that class.
For example, new variations on instances of the following class would be
considered "too complex" because those instances create more than 8
leaves in the shape tree:
```ruby
class Foo; end
9.times { Foo.new.instance_variable_set(":@uniq_#{_1}", 1) }
```
However, the following class is *not* too complex because it only has
one leaf in the shape tree:
```ruby
class Foo
def initialize
@a = @b = @c = @d = @e = @f = @g = @h = @i = nil
end
end
9.times { Foo.new }
``
This case is rare, so we don't expect this change to impact performance
of most applications, but it needs to be handled.
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
When moving Objects between size pools we have to assign a new shape.
This happened during updating references - we tried to create a new shape
tree that mirrored the existing tree, but based on the root shape of the
new size pool.
This causes allocations to happen if the new tree doesn't already exist,
potentially triggering a GC, during GC.
This commit changes object movement to look for a pre-existing new tree
during object movement, and if that tree does not exist, we don't move
the object to the new pool.
This allows us to remove the shape allocation from update references.
Co-Authored-By: Peter Zhu <peter@peterzhu.ca>
We can loosely predict the number of ivar sets on a class based on the
number of iv set instructions in the initialize method. This should give
us a more accurate estimate to use for initial size pool allocation,
which should in turn give us more cache hits.
This commit adds RVALUE_OVERHEAD for storing metadata at the end of the
slot. This commit moves the ractor_belonging_id in debug builds from the
flags to RVALUE_OVERHEAD which frees the 16 bits in the headers for
object shapes.
We would like to differentiate types of objects via their shape. This
commit adds a special T_OBJECT shape when we allocate an instance of
T_OBJECT. This allows us to avoid testing whether an object is an
instance of a T_OBJECT or not, we can just check the shape.
Peter Zhu
Takashi Kokubun
Jean Boussier
git
Matt Valentine-House
Nobuyoshi Nakada
Jean byroot Boussier
Jean Boussier
Kunshan Wang
Jemma Issroff
Mirek Klimos
Aaron Patterson