2014-06-01 13:09:10

by Real Name

Subject: [PATCH] delete unnecessary bootmem struct page array

From: Honggang Li <[email protected]>

The patch based on linux-next-20140530.

Honggang Li (1):
delete unnecessary bootmem struct page array

arch/um/kernel/um_arch.c | 6 ------
1 file changed, 6 deletions(-)

--
1.8.3.1

2014-06-01 13:09:16

by Real Name

Subject: [PATCH] delete unnecessary bootmem struct page array

From: Honggang Li <[email protected]>

1) uml kernel bootmem managed through bootmem_data->node_bootmem_map,
not the struct page array, so the array is unnecessary.

2) the bootmem struct page array has been pointed by a *local* pointer,
struct page *map, in init_maps function. The array can be accessed only
in init_maps's scope. As a result, uml kernel wastes about 1% of total
memory.

Signed-off-by: Honggang Li <[email protected]>
---
arch/um/kernel/um_arch.c | 6 ------
1 file changed, 6 deletions(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 6043c76..5aa2d82 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -338,12 +338,6 @@ int __init linux_main(int argc, char **argv)
start_vm = VMALLOC_START;

setup_physmem(uml_physmem, uml_reserved, physmem_size, highmem);
- if (init_maps(physmem_size, iomem_size, highmem)) {
- printf("Failed to allocate mem_map for %Lu bytes of physical "
- "memory and %Lu bytes of highmem\n", physmem_size,
- highmem);
- exit(1);
- }

virtmem_size = physmem_size;
stack = (unsigned long) argv;
--
1.8.3.1

2014-06-01 13:57:35

by Richard Weinberger

Subject: Re: [PATCH] delete unnecessary bootmem struct page array

Am 01.06.2014 15:08, schrieb Real Name:
> From: Honggang Li <[email protected]>
>
> 1) uml kernel bootmem managed through bootmem_data->node_bootmem_map,
> not the struct page array, so the array is unnecessary.
>
> 2) the bootmem struct page array has been pointed by a *local* pointer,
> struct page *map, in init_maps function. The array can be accessed only
> in init_maps's scope. As a result, uml kernel wastes about 1% of total
> memory.

I reread your patch again.
You missed one important point. init_maps() setups max_mapnr which is used by
virt_addr_valid().

We have to be extremely careful here to not introduce a subtle fuckup.

Thanks,
//richard