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Create SHAPE_MAX_NUM_IVS (currently 50) and limit all shapes to that
number of IVs. When a shape has more than 50 IVs, fallback to the
obj_too_complex shape which uses hash lookup for ivs.
Notes:
Merged: https://github.com/ruby/ruby/pull/7183
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Notes:
Merged: https://github.com/ruby/ruby/pull/7078
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Notes:
Merged-By: k0kubun <takashikkbn@gmail.com>
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SIZE_POOL_COUNT is a GC macro, it should belong in gc.h and not shape.h.
SIZE_POOL_COUNT doesn't depend on shape.h so we can have shape.h depend
on gc.h.
Co-Authored-By: Matt Valentine-House <matt@eightbitraptor.com>
Notes:
Merged: https://github.com/ruby/ruby/pull/6940
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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>
Notes:
Merged: https://github.com/ruby/ruby/pull/6938
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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>
Notes:
Merged: https://github.com/ruby/ruby/pull/6931
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This reverts commit 9c54466e299aa91af225bc2d92a3d7755730948f.
We're seeing crashes in Shopify CI after this commit.
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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>
Notes:
Merged: https://github.com/ruby/ruby/pull/6926
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I see several arguments in doing so.
First they use a non trivial amount of memory, so for various memory
profiling/mapping tools it is relevant to have visibility of the space
occupied by shapes.
Then, some pathological code can create a tons of shape, so it is
valuable to have a way to have a way to observe shapes without having
to compile Ruby with `SHAPE_DEBUG=1`.
And additionally it's likely much faster to dump then this way than
to use `RubyVM::Shape`.
There are however a few open questions:
- Shapes can't respect the `since:` argument. Not sure what to do when
it is provided. Would probably make sense to not dump them.
- Maybe it would make more sense to have a separate `ObjectSpace.dump_shapes`?
- Maybe instead `dump_all` should take a `shapes: false` argument?
Additionally, `ObjectSpace.dump_shapes` is added for the use case of
debugging the evolution of the shape tree.
Notes:
Merged: https://github.com/ruby/ruby/pull/6868
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Cases like this:
```ruby
obj = Object.new
loop do
obj.instance_variable_set(:@foo, 1)
obj.remove_instance_variable(:@foo)
end
```
can cause us to use many more shapes than we want (and even run out).
This commit changes the code such that when an instance variable is
removed, we'll walk up the shape tree, find the shape, then rebuild any
child nodes that happened to be below the "targetted for removal" IV.
This also requires moving any instance variables so that indexes derived
from the shape tree will work correctly.
Co-Authored-By: Jemma Issroff <jemmaissroff@gmail.com>
Co-authored-by: John Hawthorn <jhawthorn@github.com>
Notes:
Merged: https://github.com/ruby/ruby/pull/6866
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Notes:
Merged: https://github.com/ruby/ruby/pull/6767
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Notes:
Merged: https://github.com/ruby/ruby/pull/6767
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Notes:
Merged: https://github.com/ruby/ruby/pull/6767
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The ractor_belonging_id has been moved out of the headers, so object
shapes can take the top 32 bits of the flags on debug builds.
Notes:
Merged: https://github.com/ruby/ruby/pull/6763
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This commit changes the shape id comparisons to use a 32 bit comparison
rather than 64 bit. That means we don't need to load the shape id to a
register on x86 machines.
Given the following program:
```ruby
class Foo
def initialize
@foo = 1
@bar = 1
end
def read
[@foo, @bar]
end
end
foo = Foo.new
foo.read
foo.read
foo.read
foo.read
foo.read
puts RubyVM::YJIT.disasm(Foo.instance_method(:read))
```
The machine code we generated _before_ this change is like this:
```
== BLOCK 1/4, ISEQ RANGE [0,3), 65 bytes ======================
# getinstancevariable
0x559a18623023: mov rax, qword ptr [r13 + 0x18]
# guard object is heap
0x559a18623027: test al, 7
0x559a1862302a: jne 0x559a1862502d
0x559a18623030: cmp rax, 4
0x559a18623034: jbe 0x559a1862502d
# guard shape, embedded, and T_OBJECT
0x559a1862303a: mov rcx, qword ptr [rax]
0x559a1862303d: movabs r11, 0xffff00000000201f
0x559a18623047: and rcx, r11
0x559a1862304a: movabs r11, 0xb000000002001
0x559a18623054: cmp rcx, r11
0x559a18623057: jne 0x559a18625046
0x559a1862305d: mov rax, qword ptr [rax + 0x18]
0x559a18623061: mov qword ptr [rbx], rax
== BLOCK 2/4, ISEQ RANGE [3,6), 0 bytes =======================
== BLOCK 3/4, ISEQ RANGE [3,6), 47 bytes ======================
# gen_direct_jmp: fallthrough
# getinstancevariable
# regenerate_branch
# getinstancevariable
# regenerate_branch
0x559a18623064: mov rax, qword ptr [r13 + 0x18]
# guard shape, embedded, and T_OBJECT
0x559a18623068: mov rcx, qword ptr [rax]
0x559a1862306b: movabs r11, 0xffff00000000201f
0x559a18623075: and rcx, r11
0x559a18623078: movabs r11, 0xb000000002001
0x559a18623082: cmp rcx, r11
0x559a18623085: jne 0x559a18625099
0x559a1862308b: mov rax, qword ptr [rax + 0x20]
0x559a1862308f: mov qword ptr [rbx + 8], rax
```
After this change, it's like this:
```
== BLOCK 1/4, ISEQ RANGE [0,3), 41 bytes ======================
# getinstancevariable
0x5560c986d023: mov rax, qword ptr [r13 + 0x18]
# guard object is heap
0x5560c986d027: test al, 7
0x5560c986d02a: jne 0x5560c986f02d
0x5560c986d030: cmp rax, 4
0x5560c986d034: jbe 0x5560c986f02d
# guard shape
0x5560c986d03a: cmp word ptr [rax + 6], 0x19
0x5560c986d03f: jne 0x5560c986f046
0x5560c986d045: mov rax, qword ptr [rax + 0x10]
0x5560c986d049: mov qword ptr [rbx], rax
== BLOCK 2/4, ISEQ RANGE [3,6), 0 bytes =======================
== BLOCK 3/4, ISEQ RANGE [3,6), 23 bytes ======================
# gen_direct_jmp: fallthrough
# getinstancevariable
# regenerate_branch
# getinstancevariable
# regenerate_branch
0x5560c986d04c: mov rax, qword ptr [r13 + 0x18]
# guard shape
0x5560c986d050: cmp word ptr [rax + 6], 0x19
0x5560c986d055: jne 0x5560c986f099
0x5560c986d05b: mov rax, qword ptr [rax + 0x18]
0x5560c986d05f: mov qword ptr [rbx + 8], rax
```
The first ivar read is a bit more complex, but the second ivar read is
much simpler. I think eventually we could teach the context about the
shape, then emit only one shape guard.
Notes:
Merged: https://github.com/ruby/ruby/pull/6737
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Notes:
Merged: https://github.com/ruby/ruby/pull/6737
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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.
Notes:
Merged: https://github.com/ruby/ruby/pull/6758
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Notes:
Merged: https://github.com/ruby/ruby/pull/6717
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Extract an `rb_shape_get_parent` method instead of continually calling
`rb_shape_get_shape_by_id(shape->parent_id)`
Notes:
Merged: https://github.com/ruby/ruby/pull/6708
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This commit adds a `capacity` field to shapes, and adds shape
transitions whenever an object's capacity changes. Objects which are
allocated out of a bigger size pool will also make a transition from the
root shape to the shape with the correct capacity for their size pool
when they are allocated.
This commit will allow us to remove numiv from objects completely, and
will also mean we can guarantee that if two objects share shapes, their
IVs are in the same positions (an embedded and extended object cannot
share shapes). This will enable us to implement ivar sets in YJIT using
object shapes.
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Notes:
Merged: https://github.com/ruby/ruby/pull/6699
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* Avoid RCLASS_IV_TBL in marshal.c
* Avoid RCLASS_IV_TBL for class names
* Avoid RCLASS_IV_TBL for autoload
* Avoid RCLASS_IV_TBL for class variables
* Avoid copying RCLASS_IV_TBL onto ICLASSes
* Use object shapes for Class and Module IVs
Notes:
Merged-By: jhawthorn <john@hawthorn.email>
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`iv_count` is a misleading name because when IVs are unset, the new
shape doesn't decrement this value. `next_iv_count` is an accurate, and
more descriptive name.
Notes:
Merged: https://github.com/ruby/ruby/pull/6608
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Shapes provides us with an (almost) exact count of instance variables.
We only need to check for Qundef when an IV has been "undefined"
Prefer to use ROBJECT_IV_COUNT when iterating IVs
Notes:
Merged: https://github.com/ruby/ruby/pull/6555
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Prior to this commit, we were reading and writing ivar index and
shape ID in inline caches in two separate instructions when
getting and setting ivars. This meant there was a race condition
with ractors and these caches where one ractor could change
a value in the cache while another was still reading from it.
This commit instead reads and writes shape ID and ivar index to
inline caches atomically so there is no longer a race condition.
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Co-Authored-By: John Hawthorn <john@hawthorn.email>
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This reverts commit 9a6803c90b817f70389cae10d60b50ad752da48f.
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This reverts commit 68bc9e2e97d12f80df0d113e284864e225f771c2.
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Object Shapes is used for accessing instance variables and representing the
"frozenness" of objects. Object instances have a "shape" and the shape
represents some attributes of the object (currently which instance variables are
set and the "frozenness"). Shapes form a tree data structure, and when a new
instance variable is set on an object, that object "transitions" to a new shape
in the shape tree. Each shape has an ID that is used for caching. The shape
structure is independent of class, so objects of different types can have the
same shape.
For example:
```ruby
class Foo
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
class Bar
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
foo = Foo.new # `foo` has shape id 2
bar = Bar.new # `bar` has shape id 2
```
Both `foo` and `bar` instances have the same shape because they both set
instance variables of the same name in the same order.
This technique can help to improve inline cache hits as well as generate more
efficient machine code in JIT compilers.
This commit also adds some methods for debugging shapes on objects. See
`RubyVM::Shape` for more details.
For more context on Object Shapes, see [Feature: #18776]
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Co-Authored-By: Eileen M. Uchitelle <eileencodes@gmail.com>
Co-Authored-By: John Hawthorn <john@hawthorn.email>
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Revert "* expand tabs. [ci skip]"
This reverts commit 830b5b5c351c5c6efa5ad461ae4ec5085e5f0275.
Revert "This commit implements the Object Shapes technique in CRuby."
This reverts commit 9ddfd2ca004d1952be79cf1b84c52c79a55978f4.
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Object Shapes is used for accessing instance variables and representing the
"frozenness" of objects. Object instances have a "shape" and the shape
represents some attributes of the object (currently which instance variables are
set and the "frozenness"). Shapes form a tree data structure, and when a new
instance variable is set on an object, that object "transitions" to a new shape
in the shape tree. Each shape has an ID that is used for caching. The shape
structure is independent of class, so objects of different types can have the
same shape.
For example:
```ruby
class Foo
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
class Bar
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
foo = Foo.new # `foo` has shape id 2
bar = Bar.new # `bar` has shape id 2
```
Both `foo` and `bar` instances have the same shape because they both set
instance variables of the same name in the same order.
This technique can help to improve inline cache hits as well as generate more
efficient machine code in JIT compilers.
This commit also adds some methods for debugging shapes on objects. See
`RubyVM::Shape` for more details.
For more context on Object Shapes, see [Feature: #18776]
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Co-Authored-By: Eileen M. Uchitelle <eileencodes@gmail.com>
Co-Authored-By: John Hawthorn <john@hawthorn.email>
Notes:
Merged: https://github.com/ruby/ruby/pull/6386
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