Commit 688fcbfc authored by Pengfei Li's avatar Pengfei Li Committed by Linus Torvalds
Browse files

mm/vmalloc: modify struct vmap_area to reduce its size 

Objective
---------

The current implementation of struct vmap_area wasted space.

After applying this commit, sizeof(struct vmap_area) has been
reduced from 11 words to 8 words.

Description
-----------

1) Pack "subtree_max_size", "vm" and "purge_list".  This is no problem
   because

A) "subtree_max_size" is only used when vmap_area is in "free" tree

B) "vm" is only used when vmap_area is in "busy" tree

C) "purge_list" is only used when vmap_area is in vmap_purge_list

2) Eliminate "flags".

;Since only one flag VM_VM_AREA is being used, and the same thing can be
done by judging whether "vm" is NULL, then the "flags" can be eliminated.

Link: http://lkml.kernel.org/r/20190716152656.12255-3-lpf.vector@gmail.com


Signed-off-by: default avatarPengfei Li <lpf.vector@gmail.com>
Suggested-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dd3b8353

include/linux/vmalloc.h

+13 −7
Original line number Diff line number Diff line
@@ -53,15 +53,21 @@ struct vmap_area { 
	unsigned long va_start;

	unsigned long va_end;



	/*

	 * Largest available free size in subtree.

	 */

	unsigned long subtree_max_size;

	unsigned long flags;

	struct rb_node rb_node;         /* address sorted rbtree */

	struct list_head list;          /* address sorted list */

	struct llist_node purge_list;    /* "lazy purge" list */

	struct vm_struct *vm;



	/*

	 * The following three variables can be packed, because

	 * a vmap_area object is always one of the three states:

	 *    1) in "free" tree (root is vmap_area_root)

	 *    2) in "busy" tree (root is free_vmap_area_root)

	 *    3) in purge list  (head is vmap_purge_list)

	 */

	union {

		unsigned long subtree_max_size; /* in "free" tree */

		struct vm_struct *vm;           /* in "busy" tree */

		struct llist_node purge_list;   /* in purge list */

	};

};



/*

mm/vmalloc.c

+10 −14
Original line number Diff line number Diff line
@@ -329,7 +329,6 @@ EXPORT_SYMBOL(vmalloc_to_pfn); 
#define DEBUG_AUGMENT_PROPAGATE_CHECK 0

#define DEBUG_AUGMENT_LOWEST_MATCH_CHECK 0



#define VM_VM_AREA	0x04



static DEFINE_SPINLOCK(vmap_area_lock);

/* Export for kexec only */
@@ -1115,7 +1114,7 @@ retry: 


	va->va_start = addr;

	va->va_end = addr + size;

	va->flags = 0;

	va->vm = NULL;

	insert_vmap_area(va, &vmap_area_root, &vmap_area_list);



	spin_unlock(&vmap_area_lock);
@@ -1928,7 +1927,6 @@ void __init vmalloc_init(void) 
		if (WARN_ON_ONCE(!va))

			continue;



		va->flags = VM_VM_AREA;

		va->va_start = (unsigned long)tmp->addr;

		va->va_end = va->va_start + tmp->size;

		va->vm = tmp;
@@ -2026,7 +2024,6 @@ static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va, 
	vm->size = va->va_end - va->va_start;

	vm->caller = caller;

	va->vm = vm;

	va->flags |= VM_VM_AREA;

	spin_unlock(&vmap_area_lock);

}
@@ -2131,10 +2128,10 @@ struct vm_struct *find_vm_area(const void *addr) 
	struct vmap_area *va;



	va = find_vmap_area((unsigned long)addr);

	if (va && va->flags & VM_VM_AREA)

		return va->vm;



	if (!va)

		return NULL;



	return va->vm;

}



/**
@@ -2155,11 +2152,10 @@ struct vm_struct *remove_vm_area(const void *addr) 


	spin_lock(&vmap_area_lock);

	va = __find_vmap_area((unsigned long)addr);

	if (va && va->flags & VM_VM_AREA) {

	if (va && va->vm) {

		struct vm_struct *vm = va->vm;



		va->vm = NULL;

		va->flags &= ~VM_VM_AREA;

		spin_unlock(&vmap_area_lock);



		kasan_free_shadow(vm);
@@ -2862,7 +2858,7 @@ long vread(char *buf, char *addr, unsigned long count) 
		if (!count)

			break;



		if (!(va->flags & VM_VM_AREA))

		if (!va->vm)

			continue;



		vm = va->vm;
@@ -2942,7 +2938,7 @@ long vwrite(char *buf, char *addr, unsigned long count) 
		if (!count)

			break;



		if (!(va->flags & VM_VM_AREA))

		if (!va->vm)

			continue;



		vm = va->vm;
@@ -3485,10 +3481,10 @@ static int s_show(struct seq_file *m, void *p) 
	va = list_entry(p, struct vmap_area, list);



	/*

	 * s_show can encounter race with remove_vm_area, !VM_VM_AREA on

	 * behalf of vmap area is being tear down or vm_map_ram allocation.

	 * s_show can encounter race with remove_vm_area, !vm on behalf

	 * of vmap area is being tear down or vm_map_ram allocation.

	 */

	if (!(va->flags & VM_VM_AREA)) {

	if (!va->vm) {

		seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",

			(void *)va->va_start, (void *)va->va_end,

			va->va_end - va->va_start);

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