linux-kernel - Re: [rfc][patch] mm: vmap rewrite

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Date:	Fri, 06 Jun 2008 09:17:47 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Nick Piggin <npiggin@...e.de>
CC:	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [rfc][patch] mm: vmap rewrite

On 06/05/2008 12:20 PM, Nick Piggin wrote:
> Rewrite the vmap allocator to use rbtrees and lazy tlb flushing, and provide a
> fast, scalable percpu frontend for small vmaps.
[...]
> ===================================================================
> Index: linux-2.6/mm/vmalloc.c
> ===================================================================
> --- linux-2.6.orig/mm/vmalloc.c
> +++ linux-2.6/mm/vmalloc.c
[...]
> @@ -18,16 +19,17 @@
[...]
> -DEFINE_RWLOCK(vmlist_lock);
> -struct vm_struct *vmlist;
> -
> -static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
> -			    int node, void *caller);
> +/** Page table manipulation functions **/

Do not use /** for non-kdoc comments.

>  static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
>  {
[...]
> @@ -103,18 +95,24 @@ static int vmap_pte_range(pmd_t *pmd, un
>  	if (!pte)
>  		return -ENOMEM;
>  	do {
> -		struct page *page = **pages;
> -		WARN_ON(!pte_none(*pte));
> -		if (!page)
> +		struct page *page = pages[*nr];
> +
> +		if (unlikely(!pte_none(*pte))) {
> +			WARN_ON(1);
> +			return -EBUSY;
> +		}

this just may be
if (WARN_ON(!pte_none(*pte)))
   return -EBUSY;

> +		if (unlikely(!page)) {
> +			WARN_ON(1);
>  			return -ENOMEM;
> +		}

same here

>  		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
> -		(*pages)++;
> +		(*nr)++;
>  	} while (pte++, addr += PAGE_SIZE, addr != end);
>  	return 0;
>  }
[...]
> -static struct vm_struct *
> -__get_vm_area_node(unsigned long size, unsigned long flags, unsigned long start,
> -		unsigned long end, int node, gfp_t gfp_mask, void *caller)
> +
> +/** Global kva allocator **/

here too

> +static struct vmap_area *__find_vmap_area(unsigned long addr)
>  {
> -	struct vm_struct **p, *tmp, *area;
> -	unsigned long align = 1;
> +        struct rb_node *n = vmap_area_root.rb_node;

It's padded by spaces here.

> +
> +        while (n) {
> +		struct vmap_area *va;
> +
> +                va = rb_entry(n, struct vmap_area, rb_node);
> +                if (addr < va->va_start)
> +                        n = n->rb_left;
> +                else if (addr > va->va_start)
> +                        n = n->rb_right;
> +                else
> +                        return va;
> +        }
> +
> +        return NULL;
> +}
[...]
> +/** Per cpu kva allocator **/

standard /* comment */

> +#define ULONG_BITS		(8*sizeof(unsigned long))
> +#if BITS_PER_LONG < 64

Can these 2 differ?

> +/*
> + * vmap space is limited on 32 bit architectures. Ensure there is room for at
> + * least 16 percpu vmap blocks per CPU.
> + */
> +#define VMAP_BBMAP_BITS		min(1024, (128*1024*1024 / PAGE_SIZE / NR_CPUS / 16))
> +#define VMAP_BBMAP_BITS		(1024) /* 4MB with 4K pages */
> +#define VMAP_BBMAP_LONGS	BITS_TO_LONGS(VMAP_BBMAP_BITS)
> +#define VMAP_BLOCK_SIZE		(VMAP_BBMAP_BITS * PAGE_SIZE)
> +
> +struct vmap_block_queue {
> +	spinlock_t lock;
> +	struct list_head free;
> +	struct list_head dirty;
> +	unsigned int nr_dirty;
> +};
> +
> +struct vmap_block {
> +	spinlock_t lock;
> +	struct vmap_area *va;
> +	struct vmap_block_queue *vbq;
> +	unsigned long free, dirty;
> +	unsigned long alloc_map[VMAP_BBMAP_LONGS];
> +	unsigned long dirty_map[VMAP_BBMAP_LONGS];

DECLARE_BITMAP(x, VMAP_BBMAP_BITS)?
--
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