linux-kernel - Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible

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Date:	Tue, 4 May 2010 12:20:43 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Avi Kivity <avi@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	jslaby@...e.cz, akpm@...ux-foundation.org,
	paulmck@...ux.vnet.ibm.com, adobriyan@...il.com, mingo@...e.hu,
	peterz@...radead.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible

On Mon, May 3, 2010 at 5:13 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> /*
>  * Warning: if size is not a power of two, kmalloc() might
>  * waste memory because of its requirements.
>  */
> void *kvmalloc(size_t size)
> {
>        void *ptr = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
>
>        if (ptr)
>                return ptr;
>        return vmalloc(size);
> }

we can use alloc_pages_exact()/free_pages_exact() when size is larger
than PAGE_SIZE, then size isn't needed to be a power of two.

void *kvmalloc(size_t size)
{
      void *ptr;

      if (size < PAGE_SIZE)
          return kmalloc(size, GFP_KERNEL);
      ptr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
      if (ptr)
          return ptr;
      return vmalloc(size);
}

void *kvfree(void *ptr, size_t size)
{
       BUG_ON(in_interrupt());
       if (size < PAGE_SIZE)
            kfree(ptr);
       else if (is_vmalloc_addr(ptr))
            vfree(ptr);
       else
            free_pages_exact(ptr, size);
}

>
> void kvfree(void *ptr)
> {
>        BUG_ON(in_interrupt());
>        if (is_vmalloc_addr(ptr))
>                vfree(ptr);
>        else
>                kfree(ptr);
> }
>
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