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- Subject: Re: Splitting string and userdata headers from their data
- From: Mark Hamburg <mhamburg@...>
- Date: Mon, 13 Sep 2004 18:05:15 -0700
on 9/13/04 5:00 PM, Jamie Webb at email@example.com wrote:
> On Mon, Sep 13, 2004 at 08:41:36AM -0700, Mark Hamburg wrote:
>> Have any performance tests ever been done on storing string data and
>> userdata in separate memory blocks from the headers? The benefit of doing so
>> would be faster GC time since pointer-free memory wouldn't need to be
> Are you sure? Unlike something like the Boehm collector, Lua never
> needs to scan through raw data to find pointers; it knows where they
> all are.
The GC would avoid cache loads, TLB misses, and page faults to bring in data
without pointers because the relevant data for the GC would be more compact.
>> This would also make it possible to create userdata objects that managed
>> pointers they didn't allocate and shouldn't free except via the __gc
> How would that be different to storing a pointer in the userdata?
You are correct that it would be identical to what we have right now. I
guess I was thinking about it being conceptually different from the
standpoint that the Lua managed block would always hold a pointer with the
option of having that pointer freed by Lua.