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Re: VM crashes on big INBOX file ==> problem found!!!
From: |
Baoqiu Cui |
Subject: |
Re: VM crashes on big INBOX file ==> problem found!!! |
Date: |
Thu, 20 Dec 2007 14:21:04 -0800 |
Sorry for the late reply. I wanted to look deeper into the VM code but
could not find time to do that. I guess it might be easier for the new
maintainer of VM, Robert Widhopf-Fenk, to take a look at this problem
and see if there is anything that can be changed in VM. I am copying
this email to Robert...
Thanks for looking into this problem, Richard!
- Baoqiu
Richard Stallman writes:
> garbage collection is triggered and function mark_object() (in alloc.c)
> is recursively called about 29,885 times (see the backtrace info
> below)!!! So many levels of mark_object() calls make the stack
> overflow, causing a segmentation fault.
>
> I wonder if this indicates a bad choice of data structures.
> mark_object calls itself recursively for many kinds of pointers,
> but it is supposed to loop rather than recurse for cdr pointers.
> This is so that long lists do not cause recursion.
> Most data structures don't have a tremendous amount of nesting
> in the car direction.
>
> I wonder what sort of data structures made 29,885 recursive
> calls necessary. Perhaps we should change those data structures
> or else change the garbage collector so it recurses less.
>
> For instance, maybe a lot of this recursion goes thru symbols. If so,
> here is an idea. Suppose that when mark_object finds a symbol which
> is not yet marked, and is interned in the main obarray, it sets a bit
> "needs to be marked" in the symbol. Then increment a counter
> which records how many symbols are in this state.
>
> Then gc_sweep could end by scanning the main obarray over and over,
> marking those symbols, until the counter goes to zero.
>
> Depending on the nature of the problem, this might or might not
> help much. If the main data types involved are others,
> a different solution might help.
- Re: VM crashes on big INBOX file ==> problem found!!!,
Baoqiu Cui <=