Feature #9638
closed[PATCH] limit IDs to 32-bits on 64-bit systems
Description
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
Updated by normalperson (Eric Wong) over 9 years ago
sparse array is described in ruby-core:55079
Updated by normalperson (Eric Wong) over 9 years ago
I'm not sure if this is possible anymore due to SymbolGC
No big deal, though.
Updated by ngoto (Naohisa Goto) over 9 years ago
I'm using machines that have 2TB or more main memory. I think the machines can treat more than 2**32 symbols and I want to use full 64-bit capacity.
Updated by normalperson (Eric Wong) over 9 years ago
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.
Updated by normalperson (Eric Wong) over 9 years ago
- Status changed from Open to Rejected
Updated by ko1 (Koichi Sasada) over 9 years ago
(2014/03/15 4:07), normalperson@yhbt.net wrote:
Also limits symbol space to prevent OOM.
What is OOM?
Out of memory?
Symbol GC doesn't help?
--
// SASADA Koichi at atdot dot net
Updated by normalperson (Eric Wong) over 9 years ago
SASADA Koichi ko1@atdot.net wrote:
(2014/03/15 4:07), normalperson@yhbt.net wrote:
Also limits symbol space to prevent OOM.
What is OOM?
Out of memory?
Yes, out-of-memory.
Symbol GC doesn't help?
It does; but OOM was a secondary concern of mine.
I mainly wanted 32-bit ID so it might be easier to pack some structs
on 64-bit machines. 64-bit ID is not a big issue, though.
Updated by ngoto (Naohisa Goto) about 8 years ago
- Related to Feature #11420: Introduce ID key table into MRI added