Hi,
I am working on a system where we have 2GB physical RAM and we are giving 512MB to Linux Kernel(through kernel command line parameters (mem=512M) and the rest 1.5GB we are using it for local buffers.
We use using "request_mem_region" and "ioremap_nocache" kernel functions to allocate and map required buffers for our local buffers and "pci_resource_start" and "pci_ioremap_bar" to allocate and map required buffers for PCI devices.
This total (Local buffers address space + PCI devices address space) address space requirement is coming to 1256MB.
I see that system is working fine as we have vmalloc address space of 1512MB.
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With 512MB given to Linux via command line argument:
Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
vmalloc : 0xa0800000 - 0xff000000 (1512 MB)
lowmem : 0x80000000 - 0xa0000000 ( 512 MB)
pkmap : 0x7fe00000 - 0x80000000 ( 2 MB)
modules : 0x7f800000 - 0x7fe00000 ( 6 MB)
.text : 0x80008000 - 0x80434e60 (4276 kB)
.init : 0x80435000 - 0x8045e0c0 ( 165 kB)
.data : 0x80460000 - 0x8049e028 ( 249 kB)
.bss : 0x8049e030 - 0x804ce42c ( 193 kB)
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Now we have a requirement to increase Linux memory to 1GB.
I have changed the linux memory to 1GB in kernel command line and the below is the Virtual kernel memory layout for with 1GB kernel
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With 1GB given to Linux via command line argument:
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Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
vmalloc : 0xc0800000 - 0xff000000 (1000 MB)
lowmem : 0x80000000 - 0xc0000000 (1024 MB)
pkmap : 0x7fe00000 - 0x80000000 ( 2 MB)
modules : 0x7f800000 - 0x7fe00000 ( 6 MB)
.text : 0x80008000 - 0x80434e60 (4276 kB)
.init : 0x80435000 - 0x8045e0c0 ( 165 kB)
.data : 0x80460000 - 0x8049e028 ( 249 kB)
.bss : 0x8049e030 - 0x804ce42c ( 193 kB)
---------------------------------------------------------------------------------------
But i am hitting an issue here when i try to allocate and map address space to the same buffers mentioned above.
This issue is failing to allocate vmalloc regions and i see that out total requirement of address space for Local buffers + PCI Device buffers are going beyond 1000MB ( vmalloc size is 1000MB as per the above Kernel Virtual memory layout).
I was going thru some mailing lists and see that we can change user/kernel virtual split by configuring "VMSPLIT" in Linux configuration,but when i try to change it i see that kernel does not comeup and stuck at "Kernel Loading...."
Default split i see is CONFIG_VMSPLIT_2G(i.e 2G/2G, User/Kernel).
I am trying to enable CONFIG_VMSPLIT_1G (i.e 1G/3G, User/Kernel) thinking that vmalloc address space increases.
I have the following doubts which i am hoping to get clarified by someone in this forum.
a) Does address spaces in "Virtual kernel memory layout:" gets affected if i change VMSPLIT configuration in Linux?
b) What would be the reason for not booting the kernel if i change the VMSPLIT to either CONFIG_VMSPLIT_3G or CONFIG_VMSPLIT_1G?
Can someone pls through a light here as i am tired of experimenting and googling for last 2 days?
My board details:
SoC: LS1020A
DDR Size: 2GB
Linux version: 3.12.37-rt51+g43cecda
Best Regards,
Nagi
