Re: [RFC] mm: generic adaptive large memory allocation APIs

[Changli Gao <xiaosuo@gmail.com>]

On Thu, May 6, 2010 at 8:30 AM, Changli Gao <xiaosuo@gmail.com> wrote:
> kvmalloc() will try to allocate physically contiguous memory first, and try
> vmalloc to allocate virtually contiguous memory when the former allocation
> fails.
>
> kvfree() is used to free the memory allocated by kvmalloc(). It can't be used
> in atomic context. If the callers are in atomic contex, they can use
> kvfree_inatomic() instead.
>
> There is much duplicate code to do such things in kernel, so I generate the
> above APIs.
>
> Thank Eric Dumazet for the "kv" prefix. :)
>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/mm.h>
> #include <linux/init.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> #include <linux/interrupt.h>
>
> void *kvmalloc(size_t size)
> {
>        void *ptr;
>
>        if (size < PAGE_SIZE)
>                return kmalloc(PAGE_SIZE, GFP_KERNEL);
>        ptr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
>        if (ptr != NULL)
>                return ptr;
>
>        return vmalloc(size);
> }
> EXPORT_SYMBOL(kvmalloc);
>
> void kvfree(void *ptr, size_t size)
> {
>        if (size < PAGE_SIZE)
>                kfree(ptr);
>        else if (is_vmalloc_addr(ptr))
>                vfree(ptr);
>        else
>                free_pages_exact(ptr, size);
> }
> EXPORT_SYMBOL(kvfree);
>
> struct kvfree_work_struct {
>        struct work_struct      work;
>        void                    *head;
>        void                    **ptail;
> };
>
> DEFINE_PER_CPU(struct kvfree_work_struct, kvfree_work_struct);
>
> static void kvfree_work(struct work_struct *_work)
> {
>        struct kvfree_work_struct *work;
>        void *head, *tmp;
>
>        work = container_of(_work, struct kvfree_work_struct, work);
>        local_bh_disable();
>        head = work->head;
>        work->head = NULL;
>        work->ptail = &work->head;
>        local_bh_enable();

local_bh_disable should be local_irq_disable(), and local_bh_enable()
should be local_irq_enable().

>
>        while (head) {
>                tmp = head;
>                head = *(void **)head;
>                vfree(tmp);
>        }
> }
>
> void kvfree_inatomic(void *ptr, size_t size)
> {
>        if (size < PAGE_SIZE) {
>                kfree(ptr);
>        } else if (is_vmalloc_addr(ptr)) {
>                struct kvfree_work_struct *work;
>
>                *(void **)ptr = NULL;
>                local_irq_disable();
>                work = this_cpu_ptr(&kvfree_work_struct);
>                *(work->ptail) = ptr;
>                work->ptail = (void**)ptr;
>                schedule_work(&work->work);
>                local_irq_enable();
>        } else {
>                free_pages_exact(ptr, size);
>        }
> }
> EXPORT_SYMBOL(kvfree_inatomic);
>
> static int kvfree_work_struct_init(void)
> {
>        int cpu;
>        struct kvfree_work_struct *work;
>
>        for_each_possible_cpu(cpu) {
>                work = per_cpu_ptr(&kvfree_work_struct, cpu);
>                INIT_WORK(&work->work, kvfree_work);
>                work->head = NULL;
>                work->ptail = &work->head;
>        }
>
>        return 0;
> }
> //pure_initcall(kvfree_work_struct_init);
>
> //--------------------
> // for testing
> static int test_init(void)
> {
>        int size;
>        void *ptr;
>
>        kvfree_work_struct_init();
>        for (size = 1; size < (1<<30); size <<= 1) {
>                ptr = kvmalloc(size);
>                if (is_vmalloc_addr(ptr)) {
>                        printk("%d\n", size);
>                        break;
>                }
>                kvfree(ptr, size);
>        }
>
>        return 0;
> }
> module_init(test_init);
>
> static void test_exit(void)
> {
>        int cpu;
>        struct kvfree_work_struct *work;
>
>        for_each_possible_cpu(cpu) {
>                work = per_cpu_ptr(&kvfree_work_struct, cpu);
>                cancel_work_sync(&work->work);
>        }
> }
> module_exit(test_exit);
>
> MODULE_LICENSE("GPL");
>



-- 
Regards，
Changli Gao(xiaosuo@gmail.com)