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

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Date:	Fri, 7 May 2010 21:42:14 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	xiaosuo@...il.com, akpm@...ux-foundation.org
Cc:	eric.dumazet@...il.com, jslaby@...e.cz, viro@...iv.linux.org.uk,
	paulmck@...ux.vnet.ibm.com, adobriyan@...il.com, mingo@...e.hu,
	peterz@...radead.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, avi@...hat.com
Subject: Re: [RFC] mm: generic adaptive large memory allocation APIs

Changli Gao wrote:
> static void __kvfree(void *ptr, bool inatomic)

inatomic might be confusing because what vfree() checks is
BUG_ON(in_interrupt()) rather than BUG_ON(in_atomic()).

> {
>         if (unlikely(ZERO_OR_NULL_PTR(ptr)))
>                 return;
>         if (is_vmalloc_addr(ptr)) {
>                 if (inatomic) {

By the way, is in_interrupt() a heavy operation?

  register unsigned long current_stack_pointer asm("esp") __used;
  static inline struct thread_info *current_thread_info(void)
  {
  	return (struct thread_info *)
  		(current_stack_pointer & ~(THREAD_SIZE - 1));
  }
  #define preempt_count() (current_thread_info()->preempt_count)
  #define irq_count()     (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK | NMI_MASK))
  #define in_interrupt()  (irq_count())

If we can agree on changing from (inatomic) to (in_interrupt()),
we can merge kvfree() and kvfree_inatomic().

>                         struct work_struct *work;
> 
>                         work = ptr;
>                         BUILD_BUG_ON(sizeof(struct work_struct) > PAGE_SIZE);
>                         INIT_WORK(work, kvfree_work);
>                         schedule_work(work);
>                 } else {
>                         vfree(ptr);
>                 }
>         } else {
>                 struct page *page;
> 
>                 page = virt_to_head_page(ptr);
>                 if (PageSlab(page) || PageCompound(page))
>                         kfree(ptr);
>                 else
>                         free_pages_exact(ptr, page->private);
>         }
> }
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