[ruby-core:62771] [ruby-trunk - Feature #9638] [PATCH] limit IDs to 32-bits on 64-bit systems

Issue #9638 has been updated by Eric Wong.


 I am OK with closing this issue (but I'm not sure if I have permissions
 to close on redmine).
 
 However, your applications need more than 2**32 different symbols?
 That scares me :*(
 How much memory do your Ruby processes use?
 
 The Symbol table currently takes at least (48 + 48 + 40 = 136) bytes per
 symbol on 64-bit, so 136 * (2 ** 32) is 544 gigabytes just for the
 symbol table (w/fstrings) in your app.  That does not even account for
 memory of symbols with string representations longer than 23 bytes,
 nor the memory for hash table buckets.
 
 I need to know because I am also looking into using khash[1] for the
 symbol table.  By default, khash internal buckets/counters are all
 32-bits.  We can tweak khash to use 64-bit counters if needed,
 but 2**32 symbols really should be enough.
 
 The symbol table with khash might reduce memory overhead to ~90 bytes
 per-symbol on average, though...
 
 [1] git clone https://github.com/attractivechaos/klib.git
     mruby also uses khash for (all?) its hash table needs.

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Feature #9638: [PATCH] limit IDs to 32-bits on 64-bit systems
https://bugs.ruby-lang.org/issues/9638#change-46888

* Author: Eric Wong
* Status: Open
* Priority: Low
* Assignee: 
* Category: core
* Target version: current: 2.2.0
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This should allow better use of cache-friendly lookup mechanisms such as
funny_falcon's sparse array in [ruby-core:55079]

Also limits symbol space to prevent OOM.

Some structs may also be made smaller as a result (rb_method_entry_t).

We're changing ABI for 2.2.0 anyways, so this is a good time to introduce
this change.


---Files--------------------------------
0001-ID-is-always-uint32_t.patch (3.62 KB)


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