Re: [PATCH -mm v2.2] mm: get rid of __GFP_KMEMCG

From: Andrew Morton
Date: Thu Apr 10 2014 - 19:38:43 EST


On Thu, 3 Apr 2014 19:05:59 +0400 Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> wrote:

> Currently to allocate a page that should be charged to kmemcg (e.g.
> threadinfo), we pass __GFP_KMEMCG flag to the page allocator. The page
> allocated is then to be freed by free_memcg_kmem_pages. Apart from
> looking asymmetrical, this also requires intrusion to the general
> allocation path. So let's introduce separate functions that will
> alloc/free pages charged to kmemcg.
>
> The new functions are called alloc_kmem_pages and free_kmem_pages. They
> should be used when the caller actually would like to use kmalloc, but
> has to fall back to the page allocator for the allocation is large. They
> only differ from alloc_pages and free_pages in that besides allocating
> or freeing pages they also charge them to the kmem resource counter of
> the current memory cgroup.
>
> ...
>
> +void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
> +{
> + void *ret;
> + struct page *page;
> +
> + flags |= __GFP_COMP;
> + page = alloc_kmem_pages(flags, order);
> + ret = page ? page_address(page) : NULL;
> + kmemleak_alloc(ret, size, 1, flags);
> + return ret;
> +}

While we're in there it wouldn't hurt to document this: why it exists,
what it does, etc. And why it sets __GFP_COMP.

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