Re: bug of GC "step"

["Mauro Iazzi" <mauro.iazzi@...>]

This is most probably not a bug. In fact most of the consequences of
changing the GC parameters are unspecified. The manual makes it pretty
clear that you are on your own if you want to fine tune the GC.

For example, everything works here on linux, and the effect of using a
step size argument is platform dependent, as the manual says. My guess
is that using step size 0 is too small for your runtime.

I suggest that you avoid using the word "bug" for "I can't understand
what's happening" next time. I think you would have gained much more
help from the list if you did.

Mauro

2008/7/2 Makoto Hamanaka <naraxx800@yahoo.co.jp>:
> Hi,
>
> I wish any of you on this list to reply about this problem.
> Please tell me is this bug, or not? Is that case reproducable?
> I'm afraid that my report may wrong in any way.
>
>>  (1) GC "step" sometimes eat much CPU cycle than exepected, or even worse,
>>      infinitely loops under some situation.
>>  (2) GC "step" doesn't return "end of cycle" flag sometimes, when it should.
>
>
> Additionaly, I want to explain the background and another way to reproduce,
> about problem (2).
>
> What I tried to do is to take total control of GC cycles. So, I wanted to obtain
> the count of executions of collectgarbage("step") to finish a GC cycle.
> By monitoring it, I could adjust the GC values on the fly. But with this "bug",
> sometimes I can't get the count reliably.
>
> I experimented some other situations, the problem also happens
> on this GC settings.
>
> collectgarbage("setpause", 150)
> collectgarbage("setstepmul", 330)
> collectgarbage("stop")
>
> I attached the test script, and here is the output.
> This is with LuaBinaries 5.1.3 Win32 build.
>
>>lua5.1 test.lua
> =====================================
> collectgarbage("count") * 1024 = 24827 bytes
>>>>>>>>>> create static data
> collectgarbage("count") * 1024 = 38650 bytes
>>>>>>>>>> GC step
> step :  1       43533   bytes   diff:   4883    bytes
> step :  2       49210   bytes   diff:   5677    bytes
> step :  3       54071   bytes   diff:   4861    bytes
> step :  4       58932   bytes   diff:   4861    bytes
> step :  5       63772   bytes   diff:   4840    bytes
> step :  6       64188   bytes   diff:   416     bytes
> step :  7       56568   bytes   diff:   -7620   bytes
> step :  8       48950   bytes   diff:   -7618   bytes
> step :  9       50956   bytes   diff:   2006    bytes
> cycle end. step count:  9
> step :  10      55817   bytes   diff:   4861    bytes
> step :  11      60679   bytes   diff:   4862    bytes
> step :  12      65541   bytes   diff:   4862    bytes
> step :  13      70382   bytes   diff:   4841    bytes
> step :  14      75244   bytes   diff:   4862    bytes   #GC marking...
> step :  15      80085   bytes   diff:   4841    bytes
> step :  16      84926   bytes   diff:   4841    bytes
> step :  17      89767   bytes   diff:   4841    bytes
> step :  18      94608   bytes   diff:   4841    bytes
> step :  19      94932   bytes   diff:   324     bytes
> step :  20      87313   bytes   diff:   -7619   bytes
> step :  21      74896   bytes   diff:   -12417  bytes   #GC sweeping...
> step :  22      62480   bytes   diff:   -12416  bytes
> step :  23      55824   bytes   diff:   -6656   bytes <---- there should be cycle-end around here
> step :  24      60687   bytes   diff:   4863    bytes
> step :  25      65549   bytes   diff:   4862    bytes
> step :  26      70411   bytes   diff:   4862    bytes   #GC marking...
> step :  27      70932   bytes   diff:   521     bytes
> step :  28      63313   bytes   diff:   -7619   bytes
> step :  29      50896   bytes   diff:   -12417  bytes   #GC sweeping...
> step :  30      50960   bytes   diff:   64      bytes <---- also around here
> step :  31      55820   bytes   diff:   4860    bytes
> step :  32      60682   bytes   diff:   4862    bytes
> step :  33      65544   bytes   diff:   4862    bytes
> step :  34      70385   bytes   diff:   4841    bytes
> step :  35      75247   bytes   diff:   4862    bytes
> step :  36      80088   bytes   diff:   4841    bytes
> step :  37      84929   bytes   diff:   4841    bytes
> step :  38      89770   bytes   diff:   4841    bytes
> step :  39      90132   bytes   diff:   362     bytes
> step :  40      82513   bytes   diff:   -7619   bytes
> step :  41      70096   bytes   diff:   -12417  bytes
> step :  42      57680   bytes   diff:   -12416  bytes
> step :  43      55824   bytes   diff:   -1856   bytes <---- also around here
> step :  44      60687   bytes   diff:   4863    bytes
> step :  45      65549   bytes   diff:   4862    bytes
> step :  46      70411   bytes   diff:   4862    bytes
> step :  47      70932   bytes   diff:   521     bytes
> step :  48      63313   bytes   diff:   -7619   bytes
> step :  49      50896   bytes   diff:   -12417  bytes
> step :  50      50960   bytes   diff:   64      bytes <---- also around here
> collectgarbage("count") * 1024 = 51020 bytes
> collectgarbage("count") * 1024 = 36372 bytes
> =====================================
>
> So some of the end of GC cycle's are missing.
>
>
> Any insights are appreciated.
>
> Thanks,
> Makoto Hamanaka
>