The "mem" boot option can result in many unexpected consequences. This patch
attempts to prevent boot hangs which have been experienced on T4-4 and T5-8.
Basically the boot loader allocates vmlinuz and initrd higher in available
OBP physical memory. For example, on a 2Tb T5-8 it isn't possible to boot
with mem=20G.
The patch utilizes memblock to avoid reserved regions and trim memory which
is only free. Other improvements are possible for a multi-node machine.
This is a snippet of the boot log with mem=20G on T5-8 with the patch applied:
MEMBLOCK configuration: <- before memory reduction
memory size = 0x1ffad6ce000 reserved size = 0xa1adf44
memory.cnt = 0xb
memory[0x0] [0x00000030400000-0x00003fdde47fff], 0x3fada48000 bytes
memory[0x1] [0x00003fdde4e000-0x00003fdde4ffff], 0x2000 bytes
memory[0x2] [0x00080000000000-0x00083fffffffff], 0x4000000000 bytes
memory[0x3] [0x00100000000000-0x00103fffffffff], 0x4000000000 bytes
memory[0x4] [0x00180000000000-0x00183fffffffff], 0x4000000000 bytes
memory[0x5] [0x00200000000000-0x00203fffffffff], 0x4000000000 bytes
memory[0x6] [0x00280000000000-0x00283fffffffff], 0x4000000000 bytes
memory[0x7] [0x00300000000000-0x00303fffffffff], 0x4000000000 bytes
memory[0x8] [0x00380000000000-0x00383fffc71fff], 0x3fffc72000 bytes
memory[0x9] [0x00383fffc92000-0x00383fffca1fff], 0x10000 bytes
memory[0xa] [0x00383fffcb4000-0x00383fffcb5fff], 0x2000 bytes
reserved.cnt = 0x2
reserved[0x0] [0x00380000000000-0x0038000117e7f8], 0x117e7f9 bytes
reserved[0x1] [0x00380004000000-0x0038000d02f74a], 0x902f74b bytes
...
MEMBLOCK configuration: <- after reduction of memory
memory size = 0x50a1adf44 reserved size = 0xa1adf44
memory.cnt = 0x4
memory[0x0] [0x00380000000000-0x0038000117e7f8], 0x117e7f9 bytes
memory[0x1] [0x00380004000000-0x0038050d01d74a], 0x50901d74b bytes
memory[0x2] [0x00383fffc92000-0x00383fffca1fff], 0x10000 bytes
memory[0x3] [0x00383fffcb4000-0x00383fffcb5fff], 0x2000 bytes
reserved.cnt = 0x2
reserved[0x0] [0x00380000000000-0x0038000117e7f8], 0x117e7f9 bytes
reserved[0x1] [0x00380004000000-0x0038000d02f74a], 0x902f74b bytes
...
Early memory node ranges
node 7: [mem 0x380000000000-0x38000117dfff]
node 7: [mem 0x380004000000-0x380f0d01bfff]
node 7: [mem 0x383fffc92000-0x383fffca1fff]
node 7: [mem 0x383fffcb4000-0x383fffcb5fff]
Could not find start_pfn for node 0
Could not find start_pfn for node 1
Could not find start_pfn for node 2
Could not find start_pfn for node 3
Could not find start_pfn for node 4
Could not find start_pfn for node 5
Could not find start_pfn for node 6
.
The patch was tested on T4-1, T5-8 and Jalap?no.
Cc: sparclinux@vger.kernel.org
Signed-off-by: Bob Picco <bob.picco@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
7c21d533ab