[PATCH] delete unnecessary bootmem struct page array

[PATCH] delete unnecessary bootmem struct page array

[Real Name]

From: Honggang Li <enjoymindful@gmail.com>

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

[PATCH] delete unnecessary bootmem struct page array

[Real Name]

From: Honggang Li <enjoymindful@gmail.com>

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 <enjoymindful@gmail.com>
---
 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

Re: [PATCH] delete unnecessary bootmem struct page array

[Richard Weinberger]

Am 01.06.2014 15:08, schrieb Real Name:
> From: Honggang Li <enjoymindful@gmail.com>
> 
> 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

[PATCH] delete unnecessary bootmem struct page array

[Real Name]

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

2) the struct page array allocate has been pointer by a *loacl* pointer
struct page *map in init_maps function. The array can't be access after
the init_maps exit. As a result, there is about 1% of total memory leak.
---
 arch/um/kernel/um_arch.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 016adf0..9f3c6d1 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -309,11 +309,6 @@ int __init linux_main(int argc, char **argv)
 	 */
 
 	diff = UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
-	if (diff > 1024 * 1024) {
-		printf("Adding %ld bytes to physical memory to account for "
-		       "exec-shield gap\n", diff);
-		physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
-	}
 
 	uml_physmem = (unsigned long) &__binary_start & PAGE_MASK;
 
-- 
1.8.3.1

Re: [PATCH] delete unnecessary bootmem struct page array

[Real Name]

On Sun, Jun 01, 2014 at 07:34:42AM +0800, Real Name wrote:

I'm very sorry. Please ignore this email, the wrong patch had been sent
out.

> 1) uml kernel bootmem managed through bootmem_data->node_bootmem_map,
> not struct page array, so it is unnecessary.
> 
> 2) the struct page array allocate has been pointer by a *loacl* pointer
> struct page *map in init_maps function. The array can't be access after
> the init_maps exit. As a result, there is about 1% of total memory leak.
> ---
>  arch/um/kernel/um_arch.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
> index 016adf0..9f3c6d1 100644
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -309,11 +309,6 @@ int __init linux_main(int argc, char **argv)
>  	 */
>  
>  	diff = UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
> -	if (diff > 1024 * 1024) {
> -		printf("Adding %ld bytes to physical memory to account for "
> -		       "exec-shield gap\n", diff);
> -		physmem_size += UML_ROUND_UP(brk_start) - UML_ROUND_UP(&_end);
> -	}
>  
>  	uml_physmem = (unsigned long) &__binary_start & PAGE_MASK;
>  
> -- 
> 1.8.3.1
>