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net: Store virtual address instead of page in netdev_alloc_cache 

This change makes it so that we store the virtual address of the page
in the netdev_alloc_cache instead of the page pointer.  The idea behind
this is to avoid multiple calls to page_address since the virtual address
is required for every access, but the page pointer is only needed at
allocation or reset of the page.

While I was at it I also reordered the netdev_alloc_cache structure a bit
so that the size is always 16 bytes by dropping size in the case where
PAGE_SIZE is greater than or equal to 32KB.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck 2015-05-06 21:11:51 -07:00 committed by David S. Miller
parent 2ee52ad496
commit 0e39250845
2 changed files with 34 additions and 26 deletions
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5
include/linux/skbuff.h
View File

@ -2128,9 +2128,8 @@ static inline void __skb_queue_purge(struct sk_buff_head *list)
kfree_skb(skb);
}
#define NETDEV_FRAG_PAGE_MAX_ORDER get_order(32768)
#define NETDEV_FRAG_PAGE_MAX_SIZE (PAGE_SIZE << NETDEV_FRAG_PAGE_MAX_ORDER)
#define NETDEV_PAGECNT_MAX_BIAS NETDEV_FRAG_PAGE_MAX_SIZE
#define NETDEV_FRAG_PAGE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK)
#define NETDEV_FRAG_PAGE_MAX_ORDER get_order(NETDEV_FRAG_PAGE_MAX_SIZE)
void *netdev_alloc_frag(unsigned int fragsz);

55
net/core/skbuff.c
View File

@ -348,7 +348,13 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
EXPORT_SYMBOL(build_skb);
struct netdev_alloc_cache {
struct page_frag frag;
void * va;
#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
__u16 offset;
__u16 size;
#else
__u32 offset;
#endif
/* we maintain a pagecount bias, so that we dont dirty cache line
* containing page->_count every time we allocate a fragment.
*/
@ -361,21 +367,20 @@ static DEFINE_PER_CPU(struct netdev_alloc_cache, napi_alloc_cache);
static struct page *__page_frag_refill(struct netdev_alloc_cache *nc,
gfp_t gfp_mask)
{
const unsigned int order = NETDEV_FRAG_PAGE_MAX_ORDER;
struct page *page = NULL;
gfp_t gfp = gfp_mask;
if (order) {
gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
__GFP_NOMEMALLOC;
page = alloc_pages_node(NUMA_NO_NODE, gfp_mask, order);
nc->frag.size = PAGE_SIZE << (page ? order : 0);
}
#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
__GFP_NOMEMALLOC;
page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
NETDEV_FRAG_PAGE_MAX_ORDER);
nc->size = page ? NETDEV_FRAG_PAGE_MAX_SIZE : PAGE_SIZE;
#endif
if (unlikely(!page))
page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
nc->frag.page = page;
nc->va = page ? page_address(page) : NULL;
return page;
}
@ -383,19 +388,20 @@ static struct page *__page_frag_refill(struct netdev_alloc_cache *nc,
static void *__alloc_page_frag(struct netdev_alloc_cache *nc,
unsigned int fragsz, gfp_t gfp_mask)
{
struct page *page = nc->frag.page;
unsigned int size;
unsigned int size = PAGE_SIZE;
struct page *page;
int offset;
if (unlikely(!page)) {
if (unlikely(!nc->va)) {
refill:
page = __page_frag_refill(nc, gfp_mask);
if (!page)
return NULL;
/* if size can vary use frag.size else just use PAGE_SIZE */
size = NETDEV_FRAG_PAGE_MAX_ORDER ? nc->frag.size : PAGE_SIZE;
#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
/* if size can vary use size else just use PAGE_SIZE */
size = nc->size;
#endif
/* Even if we own the page, we do not use atomic_set().
* This would break get_page_unless_zero() users.
*/
@ -404,17 +410,20 @@ static void *__alloc_page_frag(struct netdev_alloc_cache *nc,
/* reset page count bias and offset to start of new frag */
nc->pfmemalloc = page->pfmemalloc;
nc->pagecnt_bias = size;
nc->frag.offset = size;
nc->offset = size;
}
offset = nc->frag.offset - fragsz;
offset = nc->offset - fragsz;
if (unlikely(offset < 0)) {
page = virt_to_page(nc->va);
if (!atomic_sub_and_test(nc->pagecnt_bias, &page->_count))
goto refill;
/* if size can vary use frag.size else just use PAGE_SIZE */
size = NETDEV_FRAG_PAGE_MAX_ORDER ? nc->frag.size : PAGE_SIZE;
#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
/* if size can vary use size else just use PAGE_SIZE */
size = nc->size;
#endif
/* OK, page count is 0, we can safely set it */
atomic_set(&page->_count, size);
@ -424,9 +433,9 @@ static void *__alloc_page_frag(struct netdev_alloc_cache *nc,
}
nc->pagecnt_bias--;
nc->frag.offset = offset;
nc->offset = offset;
return page_address(page) + offset;
return nc->va + offset;
}
static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)