This `st_table` is used to both mark and pin classes
defined from the C API. But `vm->mark_object_ary` already
does both much more efficiently.
Currently a Ruby process starts with 252 rooted classes,
which uses `7224B` in an `st_table` or `2016B` in an `RArray`.
So a baseline of 5kB saved, but since `mark_object_ary` is
preallocated with `1024` slots but only use `405` of them,
it's a net `7kB` save.
`vm->mark_object_ary` is also being refactored.
Prior to this changes, `mark_object_ary` was a regular `RArray`, but
since this allows for references to be moved, it was marked a second
time from `rb_vm_mark()` to pin these objects.
This has the detrimental effect of marking these references on every
minors even though it's a mostly append only list.
But using a custom TypedData we can save from having to mark
all the references on minor GC runs.
Addtionally, immediate values are now ignored and not appended
to `vm->mark_object_ary` as it's just wasted space.
This drops the total size of a Time object from 86 bytes to 80 bytes.
Running the benchmark benchmark/time_now.yml, this commit improves
performance of Time.now by about 30%:
```
Time.now
Branch: 13159405.4 i/s
Master: 10036908.7 i/s - 1.31x slower
Time.now(in: "+09:00")
Branch: 2712172.6 i/s
Master: 2138637.9 i/s - 1.27x slower
```
It also decreases memory usage by about 20%:
```
ary = 10_000_000.times.map { Time.now }
puts `ps -o rss= -p #{$$}`
```
Branch: 961792
Master: 1196544
Co-Authored-By: Jean Boussier <byroot@ruby-lang.org>
[Bug #19575]
struct vtm is packed causing it to have a size that is not aligned on
32-bit systems. When allocating it on the stack, it will have unaligned
addresses which means that the fields won't be marked by the GC when
scanning the stack (since the GC only marks aligned addresses). This can
cause crashes when the fields are heap allocated objects like Bignums.
This commit moves the flags in struct time_object into struct vtm for
space efficiency and removes the need for packing.
This is an example of a crash:
ruby(rb_print_backtrace+0xd) [0x56848945] ../src/vm_dump.c:785
ruby(rb_vm_bugreport) ../src/vm_dump.c:1101
ruby(rb_assert_failure+0x7a) [0x56671857] ../src/error.c:878
ruby(vm_search_cc+0x0) [0x56666e47] ../src/vm_method.c:1366
ruby(rb_vm_search_method_slowpath) ../src/vm_insnhelper.c:2090
ruby(callable_method_entry+0x5) [0x568232d3] ../src/vm_method.c:1406
ruby(rb_callable_method_entry) ../src/vm_method.c:1413
ruby(gccct_method_search_slowpath) ../src/vm_eval.c:427
ruby(gccct_method_search+0x20f) [0x568237ef] ../src/vm_eval.c:476
ruby(opt_equality_by_mid_slowpath+0x2c) [0x5682388c] ../src/vm_insnhelper.c:2338
ruby(rb_equal+0x37) [0x566fe577] ../src/object.c:133
ruby(rb_big_eq+0x34) [0x56876ee4] ../src/bignum.c:5554
ruby(rb_int_equal+0x14) [0x566f3ed4] ../src/numeric.c:4640
ruby(rb_int_equal) ../src/numeric.c:4634
ruby(vm_call0_cfunc_with_frame+0x6d) [0x568303c2] ../src/vm_eval.c:148
ruby(vm_call0_cfunc) ../src/vm_eval.c:162
ruby(vm_call0_body) ../src/vm_eval.c:208
ruby(rb_funcallv_scope+0xd1) [0x56833971] ../src/vm_eval.c:85
ruby(RB_TEST+0x0) [0x567e8488] ../src/time.c:78
ruby(eq) ../src/time.c:78
ruby(small_vtm_sub) ../src/time.c:1523
ruby(timelocalw+0x23b) [0x567f3e9b] ../src/time.c:1593
ruby(time_s_alloc+0x0) [0x567f536b] ../src/time.c:3698
ruby(time_new_timew) ../src/time.c:2694
ruby(time_s_mktime) ../src/time.c:3698
`unsigned_time_t` has the same size as `time_t`, but it doesn't mean
these types are same except for signedness. For instance, while
`long` and `long long` has the same size and `time_t` is defined as
the latter on 64bit OpenBSD, `unsigned_time_t` has been defined as
`long`.
Deletes the :include: files in doc/time, which became no longer workable when @nobu pointed out that some (but not all) creator methods accept string values as well as integer-like values.
Changes to methods:
Time.utc
Time.local
Time.at
Time.new
Since RDoc C parser cannot capture aliases which are using an
expression other than a single variable as the class, use an
intermediate variable for the singleton class.
Jean Boussier
Tanaka Akira
Nobuyoshi Nakada
Jean Boussier
Yusuke Endoh
Peter Zhu
haseponpon
Burdette Lamar
Jeremy Evans
git
Kazuki Tsujimoto
zverok
S-H-GAMELINKS
Takashi Kokubun