penformance penalty with small LUAL_BUFFERSIZE

[Martin Velek <martin.velek@...>]

Hello,

I am trying to execute(run) lua under FreeRTOS (MCU LPC2478, 512KB
Flash, 64KB internal RAM, 16MB external RAM).
Although there is plenty of external RAM, the RTOS is configured to
use only IRAM for task's stack, global variables(due to performance
reason, ERAM is used as a framebuffer or space for malloc).

The problem is, that I cannot afford tasks with 8K or more of stack
size. Looking into code, there are some functions from auxlibrary that
uses the "variable luaL_Buffer" that contains array of size =
LUAL_BUFFERSIZE =>BUFSIZ(currently 1024 on my system).

I would like to change the LUAL_BUFFERSIZE to e.g. 256 but I do not
know how much will be the performance penalty from it or even if lua
can be running with tasks less than 4K (just only simple scripts, no
recursion...).

eLua has the same behavior.

Thank you for your help.

Regards,
Martin Velek


Lua: Lua 5.1.4
Compiler: (Code)Sourcery G++
FreeRTOS: V6.0.0