Re: [PATCH 1/1] arm/module: maximum utilization of module area.

From: Vaneet Narang
Date: Mon Dec 12 2016 - 05:11:36 EST

Hi Ard,

>> +#define MODULES_START ALIGN((unsigned long)_etext - SZ_32M, PAGE_SIZE)
>On a multi_v7_defconfig kernel, the text size is >8 MB, which means
>you are only adding ~7 MB to the module area, while consuming 16 MB of
>additional address space.

I am not sure if 16MB virtual address space will make any difference on embedded
systems where physical memory is already less than virtual address space.
if required address space wastage can be reduced by keeping TASK_SIZE as
PAGE_OFFSET - 24MB like below


> Given that 20 MB modules are very uncommon,

Size of all modules can be 20MB, this seems to be normal scenario.

>I think it is better to enable CONFIG_ARM_MODULE_PLTS instead. That

CONFIG_ARM_MODULE_PLTS has function call overhead as it refers PLT table
while calling kernel functions. Also size of modules will also gets increased a bit.
So using short calls from modules to kernel will be faster.
These changes trying to utilize best available space for kernel modules for
making short calls.
So CONFIG_ARM_MODULE_PLTS is not required when modules
can be accomdated within 20MB.

>way, there is no need to update these defaults for everyone.

>> +#else

Thanks & Regards,
Vaneet Narang