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And get rid of the `obj_to_id_tbl`
It's no longer needed, the `object_id` is now stored inline
in the object alongside instance variables.
We still need the inverse table in case `_id2ref` is invoked, but
we lazily build it by walking the heap if that happens.
The `object_id` concern is also no longer a GC implementation
concern, but a generic implementation.
Co-Authored-By: Matt Valentine-House <[email protected]>
Notes:
Merged: https://github.com/ruby/ruby/pull/13159
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Using `rb_obj_clone` introduce other problems, such as `initialize_*`
callbacks invocation in the context of the parent ractor.
So we can revert back to copy the content of the object slots,
but in a way that is aware of size pools.
Notes:
Merged: https://github.com/ruby/ruby/pull/13070
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[Bug #20271]
[Bug #20267]
[Bug #20255]
`rb_obj_alloc(RBASIC_CLASS(obj))` will always allocate from the basic
40B pool, so if `obj` is larger than `40B`, we'll create a corrupted
object when we later copy the shape_id.
Instead we can use the same logic than ractor copy, which is
to use `rb_obj_clone`, and later ask the GC to free the original
object.
We then must turn it into a `T_OBJECT`, because otherwise
just changing its class to `RactorMoved` leaves a lot of
ways to keep using the object, e.g.:
```
a = [1, 2, 3]
Ractor.new{}.send(a, move: true)
[].concat(a) # Should raise, but wasn't.
```
If it turns out that `rb_obj_clone` isn't performant enough
for some uses, we can always have carefully crafted specialized
paths for the types that would benefit from it.
Notes:
Merged: https://github.com/ruby/ruby/pull/13008
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This function replaces the internal rb_obj_gc_flags API. rb_gc_object_metadata
returns an array of name and value pairs, with the last element having
0 for the name.
Notes:
Merged: https://github.com/ruby/ruby/pull/12777
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Notes:
Merged: https://github.com/ruby/ruby/pull/12546
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When reference updating ObjectSpace.trace_object_allocations, we need to
check whether the object is valid or not because it does not mark the
object so the object may be dead. This can cause a segmentation fault
if the object is on a free heap page.
For example, the following script crashes:
require "objspace"
objs = []
ObjectSpace.trace_object_allocations do
1_000_000.times do
objs << Object.new
end
end
objs = nil
# Free pages that the objs were on
GC.start
# Run compaction and check that it doesn't crash
GC.compact
Notes:
Merged: https://github.com/ruby/ruby/pull/12360
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Notes:
Merged: https://github.com/ruby/ruby/pull/12271
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We should use the rb_gc_enable/rb_gc_disable_no_rest APIs instead of
directly setting the ruby_disable_gc variable.
Notes:
Merged: https://github.com/ruby/ruby/pull/12264
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We have name fragmentation for this feature, including "shared GC",
"modular GC", and "external GC". This commit standardizes the feature
name to "modular GC" and the implementation to "GC library".
Notes:
Merged: https://github.com/ruby/ruby/pull/12261
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So that it doesn't get included in the generated binaries for builds
that don't support loading shared GC modules
Co-Authored-By: Peter Zhu <[email protected]>
Notes:
Merged: https://github.com/ruby/ruby/pull/12149
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Use PR_SET_VMA_ANON_NAME to set human-readable names for anonymous
virtual memory areas mapped by `mmap()` when compiled and run on Linux
5.17 or higher. This makes it convenient for developers to debug mmap.
Notes:
Merged: https://github.com/ruby/ruby/pull/12119
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This will add +MOD_GC to the version string and Ruby description when
Ruby is compiled with shared gc support.
When shared GC support is compiled in and a GC module has been loaded
using RUBY_GC_LIBRARY, the version string will include the name of
the currently active GC as reported by the rb_gc_active_gc_name function
in the form
+MOD_GC[gc_name]
[Feature #20794]
Notes:
Merged: https://github.com/ruby/ruby/pull/11872
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Now that we've inlined the eden_heap into the size_pool, we should
rename the size_pool to heap. So that Ruby contains multiple heaps, with
different sized objects.
The term heap as a collection of memory pages is more in memory
management nomenclature, whereas size_pool was a name chosen out of
necessity during the development of the Variable Width Allocation
features of Ruby.
The concept of size pools was introduced in order to facilitate
different sized objects (other than the default 40 bytes). They wrapped
the eden heap and the tomb heap, and some related state, and provided a
reasonably simple way of duplicating all related concerns, to provide
multiple pools that all shared the same structure but held different
objects.
Since then various changes have happend in Ruby's memory layout:
* The concept of tomb heaps has been replaced by a global free pages list,
with each page having it's slot size reconfigured at the point when it
is resurrected
* the eden heap has been inlined into the size pool itself, so that now
the size pool directly controls the free_pages list, the sweeping
page, the compaction cursor and the other state that was previously
being managed by the eden heap.
Now that there is no need for a heap wrapper, we should refer to the
collection of pages containing Ruby objects as a heap again rather than
a size pool
Notes:
Merged: https://github.com/ruby/ruby/pull/11771
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This commit splits gc.c into two files:
- gc.c now only contains code not specific to Ruby GC. This includes
code to mark objects (which the GC implementation may choose not to
use) and wrappers for internal APIs that the implementation may need
to use (e.g. locking the VM).
- gc_impl.c now contains the implementation of Ruby's GC. This includes
marking, sweeping, compaction, and statistics. Most importantly,
gc_impl.c only uses public APIs in Ruby and a limited set of functions
exposed in gc.c. This allows us to build gc_impl.c independently of
Ruby and plug Ruby's GC into itself.
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Many places call ruby_mimmalloc then MEMZERO. This can be reduced by
using ruby_mimcalloc instead.
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Co-Authored-By: Peter Zhu <[email protected]>
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This PR moves `rb_copy_wb_protected_attribute` and
`rb_gc_copy_finalizer` into a single function called
`rb_gc_copy_attributes` to be called by `init_copy`. This reduces the
surface area of the GC API.
Co-authored-by: Peter Zhu <[email protected]>
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ruby_env_debug_option gets called after Init_gc_stress, so the
--debug=gc_stress flag never works.
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It is not used anywhere else.
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It's not used outside of gc.c.
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This removes the assumption about SIZE_POOL_COUNT for shapes.
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Marking `Qnil` or `Qfalse` works fine, having
an extra macro to avoid it isn't needed.
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rb_objspace_marked_object_p is no longer used in the objspace module, so
we can remove it.
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rb_objspace_data_type_memsize is not used in the objspace module, so we
can make it private.
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I was trying to debug an (unrelated) issue in the GC, and wanted to turn
on the trace-level GC output by compiling it with -DRGENGC_DEBUG=5.
Unfortunately, this actually causes a crash in newobj_init() because the
code there tries to log the obj_info() of the newly created object.
However, the object is not actually sufficiently set up for some of the
things that obj_info() tries to do:
* The instance variable table for a class is not yet initialized, and
when using variable-length RVALUES, said ivar table is embedded in
as-yet unitialized memory after the struct RValue. Attempting to read
this, as obj_info() does, causes a crash.
* T_DATA variables need to dereference their ->type field to print out
the underlying C type name, which is not set up until newobj_fill() is
called.
To fix this, create a new method `obj_info_basic`, which dumps out only
the parts of the object that are valid before the object is fully
initialized.
[Fixes #18795]
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When generic instance variable has a shape, it is marked movable. If it
it transitions to too complex, it needs to update references otherwise
it may have incorrect references.
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Previously the growth was 3(embed), 6, 12, 24, ...
With this change it's now 3(embed), 8, 16, 32, 64, ... by default.
However, since power of two isn't the best size for all allocators,
if `malloc_usable_size` is vailable, we use it to discover the best
offset.
On Linux/glibc 2.35 for instance, the growth will be 3(embed), 7, 15, 31
to avoid wasting 8B per object.
Test program:
```c
size_t test(size_t slots) {
size_t allocated = slots * VALUE_SIZE;
void *test_ptr = malloc(allocated);
size_t wasted = malloc_usable_size(test_ptr) - allocated;
free(test_ptr);
fprintf(stderr, "slots = %lu, wasted_bytes = %lu\n", slots, wasted);
return wasted;
}
int main(int argc, char *argv[]) {
size_t best_padding = 0;
size_t padding = 0;
for (padding = 0; padding <= 2; padding++) {
size_t wasted = test(8 - padding);
if (wasted == 0) {
best_padding = padding;
break;
}
}
size_t index = 0;
fprintf(stderr, "=============== naive ================\n");
size_t list_size = 4;
for (index = 0; index < 10; index++) {
test(list_size);
list_size *= 2;
}
fprintf(stderr, "=============== auto-padded (-%lu) ================\n", best_padding);
list_size = 4;
for (index = 0; index < 10; index ++) {
test(list_size - best_padding);
list_size *= 2;
}
fprintf(stderr, "\n\n");
return 0;
}
```
```
===== glibc ======
slots = 8, wasted_bytes = 8
slots = 7, wasted_bytes = 0
=============== naive ================
slots = 4, wasted_bytes = 8
slots = 8, wasted_bytes = 8
slots = 16, wasted_bytes = 8
slots = 32, wasted_bytes = 8
slots = 64, wasted_bytes = 8
slots = 128, wasted_bytes = 8
slots = 256, wasted_bytes = 8
slots = 512, wasted_bytes = 8
slots = 1024, wasted_bytes = 8
slots = 2048, wasted_bytes = 8
=============== auto-padded (-1) ================
slots = 3, wasted_bytes = 0
slots = 7, wasted_bytes = 0
slots = 15, wasted_bytes = 0
slots = 31, wasted_bytes = 0
slots = 63, wasted_bytes = 0
slots = 127, wasted_bytes = 0
slots = 255, wasted_bytes = 0
slots = 511, wasted_bytes = 0
slots = 1023, wasted_bytes = 0
slots = 2047, wasted_bytes = 0
```
```
========== jemalloc =======
slots = 8, wasted_bytes = 0
=============== naive ================
slots = 4, wasted_bytes = 0
slots = 8, wasted_bytes = 0
slots = 16, wasted_bytes = 0
slots = 32, wasted_bytes = 0
slots = 64, wasted_bytes = 0
slots = 128, wasted_bytes = 0
slots = 256, wasted_bytes = 0
slots = 512, wasted_bytes = 0
slots = 1024, wasted_bytes = 0
slots = 2048, wasted_bytes = 0
=============== auto-padded (-0) ================
slots = 4, wasted_bytes = 0
slots = 8, wasted_bytes = 0
slots = 16, wasted_bytes = 0
slots = 32, wasted_bytes = 0
slots = 64, wasted_bytes = 0
slots = 128, wasted_bytes = 0
slots = 256, wasted_bytes = 0
slots = 512, wasted_bytes = 0
slots = 1024, wasted_bytes = 0
slots = 2048, wasted_bytes = 0
```
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WeakMap can crash during compaction because the st_insert could allocate
memory.
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