linux-kernel - Re: [PATCH 1/9] mm: add generic adaptive large memory allocation APIs

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Message-ID: <1273756816.5605.3547.camel@twins>
Date:	Thu, 13 May 2010 15:20:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	akpm@...ux-foundation.org, Hoang-Nam Nguyen <hnguyen@...ibm.com>,
	Christoph Raisch <raisch@...ibm.com>,
	Roland Dreier <rolandd@...co.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Divy Le Ray <divy@...lsio.com>,
	"James E.J. Bottomley" <James.Bottomley@...e.de>,
	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger@....com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Paul Menage <menage@...gle.com>,
	Li Zefan <lizf@...fujitsu.com>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	containers@...ts.linux-foundation.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [PATCH 1/9] mm: add generic adaptive large memory allocation
 APIs

On Thu, 2010-05-13 at 17:51 +0800, Changli Gao wrote:
> +void *__kvmalloc(size_t size, gfp_t flags)
> +{
> +       void *ptr;
> +
> +       if (size < PAGE_SIZE)
> +               return kmalloc(size, GFP_KERNEL | flags);
> +       size = PAGE_ALIGN(size);
> +       if (is_power_of_2(size))
> +               ptr = (void *)__get_free_pages(GFP_KERNEL | flags |
> +                                              __GFP_NOWARN, get_order(size));
> +       else
> +               ptr = alloc_pages_exact(size, GFP_KERNEL | flags |
> +                                             __GFP_NOWARN);
> +       if (ptr != NULL) {
> +               virt_to_head_page(ptr)->private = size;
> +               return ptr;
> +       }
> +
> +       ptr = vmalloc(size);
> +       if (ptr != NULL && (flags & __GFP_ZERO))
> +               memset(ptr, 0, size);
> +
> +       return ptr;
> +}
> +EXPORT_SYMBOL(__kvmalloc);

So if I do kvmalloc(size, GFP_ATOMIC) I get GFP_KERNEL|GFP_ATOMIC, which
is not a recommended variation because one should not mix __GFP_WAIT and
__GFP_HIGH.

So I would simply drop the gfp argument to avoid confusion.

> +void __kvfree(void *ptr, bool inatomic)
> +{
> +       if (unlikely(ZERO_OR_NULL_PTR(ptr)))
> +               return;
> +       if (is_vmalloc_addr(ptr)) {
> +               if (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 if (is_power_of_2(page->private))
> +                       free_pages((unsigned long)ptr,
> +                                  get_order(page->private));
> +               else
> +                       free_pages_exact(ptr, page->private);
> +       }
> +}
> +EXPORT_SYMBOL(__kvfree); 

NAK, I really utterly dislike that inatomic argument. The alloc side
doesn't function in atomic context either. Please keep the thing
symmetric in that regards.
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