Choosing better HASH_BIAS
- From: Юрий Соколов <funny.falcon@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 6 Sep 2013 19:54:08 +0400
Hello,
Benching one of homegrown software it were discovered, that it spends
measurable amount of time in lua_obj_equal cause of calling to ffi.gc .
(linux x86_64)
It looks like setting HASH_BIAS to 0 gives less collisions in finalizers
table.
Testing script: http://pastebin.com/6vzisjBa
Results:
With current HASH_BIAS:
$ time luajit test_gc.lua 10000000
10000000
real 0m5.735s
user 0m5.496s
sys 0m0.232s
With HASH_BIAS (0x0):
$ time luajit test_gc.lua 10000000
10000000
real 0m4.800s
user 0m4.532s
sys 0m0.264s
Perhaps, more adequate value for HASH_BIAS exists (for example, 0x10100000
is good for some patterns),
but current value is definitely bad.
With regards,
Sokolov Yura aka funny_falcon
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