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Force recycle intermediate collection in Hash#transform_keys! #4329

Merged
merged 2 commits into from
Mar 28, 2021
Merged

Force recycle intermediate collection in Hash#transform_keys! #4329

merged 2 commits into from
Mar 28, 2021

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kachick
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@kachick kachick commented Mar 28, 2021 •
edited

This PR might be just a question 🙇

ruby/hash.c

Lines 4389 to 4411 in fb6ebe5

static VALUE
rb_hash_compare_by_id(VALUE hash)
{
VALUE tmp;
st_table *identtable;
if (rb_hash_compare_by_id_p(hash)) return hash;
rb_hash_modify_check(hash);
ar_force_convert_table(hash, __FILE__, __LINE__);
HASH_ASSERT(RHASH_ST_TABLE_P(hash));
tmp = hash_alloc(0);
identtable = rb_init_identtable_with_size(RHASH_SIZE(hash));
RHASH_ST_TABLE_SET(tmp, identtable);
rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)tmp);
st_free_table(RHASH_ST_TABLE(hash));
RHASH_ST_TABLE_SET(hash, identtable);
RHASH_ST_CLEAR(tmp);
rb_gc_force_recycle(tmp);
return hash;
}
looks using this function for the intermediate hash.
So this code needs to same way...? 🤔 (I'm not sure, how to check the changed behaviors in ruby code layer...)

ref: #4294, 5e5fb72

@nobu Could you review? 🙏

@nobu
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nobu commented Mar 28, 2021

As rb_hash_compare_by_id replaces the ST table with a different type of ST, it is complicated.
An empty Hash would not be a GC pressure so much though, it is better to have.
Ditto for the array pairs.

@kachick kachick changed the title Force recycle intermediate hash [Bug #17735] Force recycle intermediate collection Mar 28, 2021
@kachick kachick changed the title Force recycle intermediate collection Force recycle intermediate collection in Hash#transform_keys! Mar 28, 2021
@kachick
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kachick commented Mar 28, 2021

Thank you for letting me know! 😂
So added for pairs too f435edd

@nobu nobu merged commit 522d4cd into ruby:master Mar 28, 2021
@kachick
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kachick commented Mar 28, 2021

Thank you!

@kachick kachick deleted the tmp-hash-force-gc branch March 28, 2021 05:21
@ko1
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ko1 commented Mar 31, 2021

Please Do not use force_recycle because it is an exceptional operation and slow, now a day . It can violate GC assumptions. I wanted to make it no-op, but I couldn't make it because some code depends on this behavior.

@kachick kachick mentioned this pull request Mar 31, 2021
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kachick commented Mar 31, 2021

🙇

Please Do not use force_recycle because it is an exceptional operation and slow, now a day . It can violate GC assumptions. I wanted to make it no-op, but I couldn't make it because some code depends on this behavior.

I should note it. Thanks for your alerting 🙏

I have created a PR to just revert this as #4341. Please merge it if it is needed.

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ko1 commented Apr 1, 2021

Thank you for your quick patch. It was not your fault, because it is not noted anywhere.
Anyway, thanks again.

matzbot pushed a commit that referenced this pull request Apr 15, 2021
@nagachika
merge revision(s) 31e0382,5e5fb72f99701dc27c66ab148471893f14e6d6f0,fb…
84d9a9a 
…6ebe55d91187d9635e0183d47dbf38e95b1141,522d4cd32f7727886f4fcbc28ed29c08d361ee20: [Backport #17735]

	Keep non evaluated keys in `Hash#transform_keys!` [Bug #17735]

	---
	 hash.c                                     |  6 +++++-
	 spec/ruby/core/hash/transform_keys_spec.rb | 12 +++++++++++-
	 test/ruby/test_hash.rb                     |  8 ++++++++
	 3 files changed, 24 insertions(+), 2 deletions(-)

	Clear an intermediate hash [Bug #17735]

	---
	 hash.c | 1 +
	 1 file changed, 1 insertion(+)

	Hide an intermediate array

	---
	 hash.c | 6 ++++--
	 1 file changed, 4 insertions(+), 2 deletions(-)

	Force recycle intermediate collection in Hash#transform_keys! [Bug
	 #17735]

	* Force recycle intermediate hash

	* Force recycle intermediate array too

	#4329 (comment)
	---
	 hash.c | 2 ++
	 1 file changed, 2 insertions(+)
@peterzhu2118 peterzhu2118 mentioned this pull request Oct 12, 2021
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@nobu nobu nobu approved these changes

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