[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 v2] delete unnecessary bootmem struct page array

[Real Name]

From: Honggang Li <enjoymindful@gmail.com>

The patch based on linux-next-2014-06-02.

The old init_maps function does two things:
1) allocates and initializes one struct page array for bootmem
2) count the number of total pages

After removed the source code related to the unnecessary array, the name 
'init_maps' is some kind of improper named, as it just count the number of
total page numbers. So, I renamed the function as 'mem_total_pages'.

I tested the patch through repeat reboot the uml kernel many times.
[real@name linux-next]$ make ARCH=um defconfig
[real@name linux-next]$ make ARCH=um linux
[real@name linux-next]$ file linux
linux: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, not stripped
[real@name linux-next]$ ./linux ubda=/home/real/linux-next/Fedora20-AMD64-root_fs mem=256m && sync && echo 1
[real@name linux-next]$ ./linux ubda=/home/real/linux-next/Fedora20-AMD64-root_fs mem=256m && sync && echo 2
(repeat reboot the uml kernel many times..)

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

 arch/um/include/shared/mem_user.h |  2 +-
 arch/um/kernel/physmem.c          | 32 ++++++--------------------------
 arch/um/kernel/um_arch.c          |  7 +------
 3 files changed, 8 insertions(+), 33 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/include/shared/mem_user.h |  2 +-
 arch/um/kernel/physmem.c          | 32 ++++++--------------------------
 arch/um/kernel/um_arch.c          |  7 +------
 3 files changed, 8 insertions(+), 33 deletions(-)

diff --git a/arch/um/include/shared/mem_user.h b/arch/um/include/shared/mem_user.h
index 46384ac..cb84414 100644
--- a/arch/um/include/shared/mem_user.h
+++ b/arch/um/include/shared/mem_user.h
@@ -49,7 +49,7 @@ extern int iomem_size;
 extern int init_mem_user(void);
 extern void setup_memory(void *entry);
 extern unsigned long find_iomem(char *driver, unsigned long *len_out);
-extern int init_maps(unsigned long physmem, unsigned long iomem,
+extern void mem_total_pages(unsigned long physmem, unsigned long iomem,
 		     unsigned long highmem);
 extern unsigned long get_vm(unsigned long len);
 extern void setup_physmem(unsigned long start, unsigned long usable,
diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index 30fdd5d..549ecf3 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -22,39 +22,19 @@ EXPORT_SYMBOL(high_physmem);
 
 extern unsigned long long physmem_size;
 
-int __init init_maps(unsigned long physmem, unsigned long iomem,
+void __init mem_total_pages(unsigned long physmem, unsigned long iomem,
 		     unsigned long highmem)
 {
-	struct page *p, *map;
-	unsigned long phys_len, phys_pages, highmem_len, highmem_pages;
-	unsigned long iomem_len, iomem_pages, total_len, total_pages;
-	int i;
-
-	phys_pages = physmem >> PAGE_SHIFT;
-	phys_len = phys_pages * sizeof(struct page);
-
-	iomem_pages = iomem >> PAGE_SHIFT;
-	iomem_len = iomem_pages * sizeof(struct page);
+	unsigned long phys_pages, highmem_pages;
+	unsigned long iomem_pages, total_pages;
 
+	phys_pages    = physmem >> PAGE_SHIFT;
+	iomem_pages   = iomem   >> PAGE_SHIFT;
 	highmem_pages = highmem >> PAGE_SHIFT;
-	highmem_len = highmem_pages * sizeof(struct page);
-
-	total_pages = phys_pages + iomem_pages + highmem_pages;
-	total_len = phys_len + iomem_len + highmem_len;
 
-	map = alloc_bootmem_low_pages(total_len);
-	if (map == NULL)
-		return -ENOMEM;
-
-	for (i = 0; i < total_pages; i++) {
-		p = &map[i];
-		memset(p, 0, sizeof(struct page));
-		SetPageReserved(p);
-		INIT_LIST_HEAD(&p->lru);
-	}
+	total_pages   = phys_pages + iomem_pages + highmem_pages;
 
 	max_mapnr = total_pages;
-	return 0;
 }
 
 void map_memory(unsigned long virt, unsigned long phys, unsigned long len,
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 6043c76..dbd5bda 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -338,12 +338,7 @@ 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);
-	}
+	mem_total_pages(physmem_size, iomem_size, highmem);
 
 	virtmem_size = physmem_size;
 	stack = (unsigned long) argv;
-- 
1.8.3.1

[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 | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 016adf0..d4c98d1 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -348,12 +348,6 @@ 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]

Hi!

Am 01.06.2014 02:24, schrieb 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.

Please add a Signed-off-by tag using your real name.

Thanks,
//richard

> ---
>  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 016adf0..d4c98d1 100644
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -348,12 +348,6 @@ 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;
> 

[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
>