On 32-bit systems, we must store the shape ID in the gen_ivtbl to not
lose the shape. If we directly store the ST table into the generic
ivar table, then we lose the shape. This makes it impossible to
determine the shape of the object and whether it is too complex or not.
This patch introduce M:N thread scheduler for Ractor system.
In general, M:N thread scheduler employs N native threads (OS threads)
to manage M user-level threads (Ruby threads in this case).
On the Ruby interpreter, 1 native thread is provided for 1 Ractor
and all Ruby threads are managed by the native thread.
From Ruby 1.9, the interpreter uses 1:1 thread scheduler which means
1 Ruby thread has 1 native thread. M:N scheduler change this strategy.
Because of compatibility issue (and stableness issue of the implementation)
main Ractor doesn't use M:N scheduler on default. On the other words,
threads on the main Ractor will be managed with 1:1 thread scheduler.
There are additional settings by environment variables:
`RUBY_MN_THREADS=1` enables M:N thread scheduler on the main ractor.
Note that non-main ractors use the M:N scheduler without this
configuration. With this configuration, single ractor applications
run threads on M:1 thread scheduler (green threads, user-level threads).
`RUBY_MAX_CPU=n` specifies maximum number of native threads for
M:N scheduler (default: 8).
This patch will be reverted soon if non-easy issues are found.
[Bug #19842]
`rb_current_ractor()` expects it has valid `ec` and `r`.
`rb_current_ractor_raw()` with a parameter `false` allows to return
NULL if `ec` is not available.
st tables will maintain insertion order so we can marshal dump / load
objects with instance variables in the same order they were set on that
particular instance
[ruby-core:112926] [Bug #19535]
Co-Authored-By: Jemma Issroff <jemmaissroff@gmail.com>
A variable modified in `EXEC_TAG` block should be `volatile`.
```
ractor.c: In function 'ractor_try_yield':
ractor.c:1251:97: warning: argument 'obj' might be clobbered by 'longjmp' or 'vfork' [-Wclobbered]
1251 | ractor_try_yield(rb_execution_context_t *ec, rb_ractor_t *cr, struct rb_ractor_queue *ts, VALUE obj, VALUE move, bool exc, bool is_will)
| ~~~~~~^~~
```
passing will and closing notification can conflict and
`Ractor::Selector#empty?` can return wrong answer.
This patch fix it.
```
s = Ractor::Selector.new
s.add Ractor.new{10}
s.add Ractor.new{20}
r, v = s.wait
vs = []
vs << v
r, v = s.wait
vs << v
[*vs.sort, s.empty?]
#=> "[10, 20, false]" (expected "[10, 20, true]")
```
This patch rewrites Ractor synchronization mechanism, send/receive
and take/yield.
* API
* Ractor::Selector is introduced for lightweight waiting
for many ractors.
* Data structure
* remove `struct rb_ractor_waiting_list` and use
`struct rb_ractor_queue takers_queue` to manage takers.
* remove `rb_ractor_t::yield_atexit` and use
`rb_ractor_t::sync::will_basket::type` to check the will.
* add `rb_ractor_basket::p.take` to represent a taking ractor.
* Synchronization protocol
* For the Ractor local GC, `take` can not make a copy object
directly so ask to generate the copy from the yielding ractor.
* The following steps shows what `r1.take` does on `r0`.
* step1: (r0) register `r0` into `r1`'s takers.
* step2: (r0) check `r1`'s status and wakeup r0 if `r1` is waiting
for yielding a value.
* step3: (r0) sleep until `r1` wakes up `r0`.
* The following steps shows what `Ractor.yield(v)` on `r1`.
* step1: (r1) check first takers of `r1` and if there is (`r0`),
make a copy object of `v` and pass it to `r0` and
wakes up `r0`.
* step2: (r1) if there is no taker ractors, sleep until
another ractor try to take.
I noticed this while running test_yjit with --mjit-call-threshold=1,
which redefines `Integer#<`. When Ruby is monkey-patched,
MJIT itself could be broken.
Similarly, Ruby scripts could break MJIT in many different ways. I
prepared the same set of hooks as YJIT so that we could possibly
override it and disable it on those moments. Every constant under
RubyVM::MJIT is private and thus it's an unsupported behavior though.
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>
The internal location in ractor.rb is not usefull at all.
```
$ ruby -e 'Ractor.new {}'
<internal:ractor>:267: warning: Ractor is experimental, ...
```
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
Clang says "warning: variable 'pcnt' set but not used" here. In fact it
doesn't. The intention is clear that we want to increment cnt, not pcnt.
Adding a * mark solves everything.
Ractor verification requires storing the ractor id in the top 32 bits of
the object header. Unfortunately 32 bit machines only have 32 bits in
the object header. The verification code has a 32 bit left shift which
doesn't work on i686 and will clobber existing flags.
This commit disables the verification code on i686 since i686 will crash
if it's enabled.
Co-Authored-By: John Hawthorn <john@hawthorn.email>
Co-Authored-By: Jemma Issroff <jemmaissroff@gmail.com>
Now GVL is not process *Global* so this patch try to use
another words.
* `rb_global_vm_lock_t` -> `struct rb_thread_sched`
* `gvl->owner` -> `sched->running`
* `gvl->waitq` -> `sched->readyq`
* `rb_gvl_init` -> `rb_thread_sched_init`
* `gvl_destroy` -> `rb_thread_sched_destroy`
* `gvl_acquire` -> `thread_sched_to_running` # waiting -> ready -> running
* `gvl_release` -> `thread_sched_to_waiting` # running -> waiting
* `gvl_yield` -> `thread_sched_yield`
* `GVL_UNLOCK_BEGIN` -> `THREAD_BLOCKING_BEGIN`
* `GVL_UNLOCK_END` -> `THREAD_BLOCKING_END`
* removed
* `rb_ractor_gvl`
* `rb_vm_gvl_destroy` (not used)
There are GVL functions such as `rb_thread_call_without_gvl()` yet
but I don't have good name to replace them. Maybe GVL stands for
"Greate Valuable Lock" or something like that.
I have this scripts that deadlocks after about
5 minutes if I repeatedly run it with a shell loop:
```ruby
$VERBOSE = nil
lamb = ->(main, gc) do
gc.verify_internal_consistency
gc.verify_internal_consistency
main << 1
gc.verify_internal_consistency
gc.verify_internal_consistency
main << 2
gc.verify_internal_consistency
gc.verify_internal_consistency
main << 3
gc.verify_internal_consistency
gc.verify_internal_consistency
end
lamb[[], GC]
lamb[[], GC]
r = Ractor.new Ractor.current, GC, &lamb
a = []
a << Ractor.receive_if{|msg| msg == 2}
a << Ractor.receive_if{|msg| msg == 3}
a << Ractor.receive_if{|msg| msg == 1}
```
Shell loop:
```shell
while ./miniruby deadlock.rb; do date; done
```
Once it locks up, CTRL-C doesn't interrupt the process which
led me to infer `receive_if` is looping in `ractor_receive_if()`
without checking for interrupts. This can be confirmed by
attaching a debugger to the deadlocked miniruby.
The deadlock has one thread looping in `receive_if`
and another waiting in `rb_vm_barrier()`. The barrier relies
on interrupt checking to finish. Theoretically speaking the
`rb_vm_barrier()` could come from one thread naturally starting GC.
We found this while developing YJIT but it dead locks running
with YJIT disabled. YJIT currently relies on `rb_vm_barrier()`
to synchronize before changing memory protection.
This diff adds an interrupt check in the loop in `Ractor#receive_if`
which seems to fix the deadlock.
In addition, this commit allows interrupting the following single
ractor script with CTRL-C.
```shell
ruby -e 'Ractor.current.send(3); Ractor.receive_if { false }'
```
`USE_RUBY_DEBUG_LOG` was only defined when `RUBY_DEVEL` is defined.
This patch removes this dependency (`USE_RUBY_DEBUG_LOG` is defined
independently from `RUBY_DEVEL`).
Do not commit a patch which enables `USE_RUBY_DEBUG_LOG`.
* ujit: implement opt_getinlinecache
Aggressively bet that writes to constants don't happen and invalidate
all opt_getinlinecache blocks on any and all constant writes.
Use alignment padding on block_t to track this assumption. No change to
sizeof(block_t).
* Fix compile warnings when not RUBY_DEBUG
* Fix reversed condition
* Switch to st_table to keep track of assumptions
Co-authored-by: Aaron Patterson <aaron.patterson@gmail.com>
Co-authored-by: Maxime Chevalier-Boisvert <maximechevalierb@gmail.com>
rb_objspace_reachable_objects_from requires that the GC not be active.
Since the Ractor barrier is not executed for incremental sweeping,
Ractor may call rb_objspace_reachable_objects_from after sweeping
has started to share objects. This causes a crash that looks like
the following:
```
<internal:ractor>:627: [BUG] rb_objspace_reachable_objects_from() is not supported while during_gc == true
```
Co-authored-by: Vinicius Stock <vinicius.stock@shopify.com>
When a Ractor is removed, the freelist in the Ractor cache is not
returned to the GC, leaving the freelist permanently lost. This commit
recycles the freelist when the Ractor is destroyed, preventing a memory
leak from occurring.
If the GC has been disabled we need to re-enable it so we can evacuate
the transient heap.
Fixes https://bugs.ruby-lang.org/issues/17985
[Bug #17985] [ruby-core:104260]
Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>
Peter Zhu
Koichi Sasada
S-H-GAMELINKS
Nobuyoshi Nakada
Aaron Patterson
Takashi Kokubun
Matt Valentine-House
Jemma Issroff
卜部昌平
Yusuke Endoh
Alan Wu
Jose Narvaez
Kazuhiro NISHIYAMA
eileencodes
Ryuta Kamizono