question about memory allocation for DM8168

1330hayacool7102

After looking the DM8168_DVR_RDK_Install_Guide.pdf with Version 02.00.00.xx,

2.1.1 Build configuration for 256MB allocation to Linux kernel
 Open and edit <DVR_RDK_BASE>/dvr_rdk/Rules.make
 Modify LINUX_MEM to LINUX_MEM_256M in place of LINUX_MEM_128M
 Linux memory has to be set to 242M in the bootargs
 Default build configuration is set to 128MB for linux kernel memory
 When using 128MB linux configuration, build configuration needs to be set to 116M in the bootargs

==> why the bootargs is 242M instead of 256MB in case of 256MB allocation to linux kernel? why the bootargs is116M instead of 128MB in case of 128MB allocation to linux kernel

over 13 years ago

0 Ivan Nardi over 13 years ago

Intellectual 445 points

in my opinion, because same memory is reserved for the frame buffer via "vram=..." parameters in bootargs.

Ivan

0 1330hayacool7102 over 13 years ago in reply to Ivan Nardi

Guru 10655 points

The vram is always 20M for both case. 20M , 242M, 256M ? Till now, I have no idea about their relationship.... Any idea?

0 1330hayacool7102 over 13 years ago in reply to 1330hayacool7102

Guru 10655 points

who can explain this for us?

0 HardikShah over 13 years ago in reply to 1330hayacool7102

TI__Mastermind 20245 points

Hi,

VRAM allocates memory from Linux memory. So if you set mem=128MB and vram=20MB then total available memroy to Linux is 128M and out of that 20M is allocated for VRAM. Thats why VRAM never changes.

Regards,

Hardik Shah

0 Joern over 13 years ago in reply to HardikShah

Genius 3055 points

Hardik,

in my opinion the problem is not to understand that VRAM might need the same amount of memory reserved for it at both configuration variants. The problem for me is more some inconsistency within the documents. It is not always completely clear and obvious how values being recommended to set have been evaluated. But to get an deeper understanding that is essential. So, again, besides clarification for what that differencies actually are needed at: Is there an explanation for the concrete amount of the suggested differences? 256M-242M is not the same as 128M-116M nor is one of these equal to 20M. I mean, that this is the core of the question.

Regards,
Joern.

0 Yogesh Marathe over 13 years ago in reply to Joern

TI__Expert 7765 points

Guys,

You can refer to the memory map to find an answer why linux memory has been changed. You can either look at generated .map files at dvr_rdk/build/dvr_rdk/bin/ti816x-evm/ or .bld in dvr_rdk/mcfw/src_bios6/cfg/ti816x which defines memory map for slave cores based on platforms. This will enable you to vitualize what is the size of each section in the entire memory map.

Usually, Linux memory is increased or reduced based on usecase. For example, if your earlier usecase was fitting in with 256 M linux memory, after few enhancements to the same usecase you may find you are running out of memory for m3 / dsp so you end up in reducing linux memory and eventually giving it to m3 / dsp as per the requirement. This is just an example.

Please let me know if this answers your question.

Regards,

Yogesh.

0 arvin arvin over 12 years ago in reply to Yogesh Marathe

Intellectual 680 points

I have the same question with Jack, why some doc request us to set bootargs mem=242M? ex...242M+20 bigger than 256M!!!

0 Badri Narayanan over 12 years ago in reply to arvin arvin

TI__Guru 59700 points

Which DVR RDK release are you using.The requirement to set LINUX to 242M has been resolved a long time ago. Pls migrate to DVR RDK 3.5 where you can use Linux mem=256M