From: Pengfei Li <lpf.vector@xxxxxxxxx> Subject: 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@xxxxxxxxx Signed-off-by: Pengfei Li <lpf.vector@xxxxxxxxx> Suggested-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Cc: Hillf Danton <hdanton@xxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/vmalloc.h | 20 +++++++++++++------- mm/vmalloc.c | 24 ++++++++++-------------- 2 files changed, 23 insertions(+), 21 deletions(-) --- a/include/linux/vmalloc.h~mm-vmalloc-modify-struct-vmap_area-to-reduce-its-size +++ a/include/linux/vmalloc.h @@ -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 */ + }; }; /* --- a/mm/vmalloc.c~mm-vmalloc-modify-struct-vmap_area-to-reduce-its-size +++ a/mm/vmalloc.c @@ -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_s 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 voi 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 NULL; + return va->vm; } /** @@ -2155,11 +2152,10 @@ struct vm_struct *remove_vm_area(const v 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, unsign 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, unsig 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, vo 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); _
