diff options
| author | Eric Dumazet | 2011-10-13 07:28:54 +0000 |
|---|---|---|
| committer | David S. Miller | 2011-10-13 16:05:07 -0400 |
| commit | 87fb4b7b533073eeeaed0b6bf7c2328995f6c075 (patch) | |
| tree | be4b37f08d7fe2d018ae68bae4577b1b2bafd0fc /net/core | |
| parent | 97ba0eb64ca690165f945a83e609102fcefa99cb (diff) | |
net: more accurate skb truesize
skb truesize currently accounts for sk_buff struct and part of skb head.
kmalloc() roundings are also ignored.
Considering that skb_shared_info is larger than sk_buff, its time to
take it into account for better memory accounting.
This patch introduces SKB_TRUESIZE(X) macro to centralize various
assumptions into a single place.
At skb alloc phase, we put skb_shared_info struct at the exact end of
skb head, to allow a better use of memory (lowering number of
reallocations), since kmalloc() gives us power-of-two memory blocks.
Unless SLUB/SLUB debug is active, both skb->head and skb_shared_info are
aligned to cache lines, as before.
Note: This patch might trigger performance regressions because of
misconfigured protocol stacks, hitting per socket or global memory
limits that were previously not reached. But its a necessary step for a
more accurate memory accounting.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Andi Kleen <ak@linux.intel.com>
CC: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/skbuff.c | 18 | ||||
| -rw-r--r-- | net/core/sock.c | 2 |
2 files changed, 15 insertions, 5 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 5b2c5f1d4dba..a7f855dca922 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -184,11 +184,20 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, goto out; prefetchw(skb); - size = SKB_DATA_ALIGN(size); - data = kmalloc_node_track_caller(size + sizeof(struct skb_shared_info), - gfp_mask, node); + /* We do our best to align skb_shared_info on a separate cache + * line. It usually works because kmalloc(X > SMP_CACHE_BYTES) gives + * aligned memory blocks, unless SLUB/SLAB debug is enabled. + * Both skb->head and skb_shared_info are cache line aligned. + */ + size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); + data = kmalloc_node_track_caller(size, gfp_mask, node); if (!data) goto nodata; + /* kmalloc(size) might give us more room than requested. + * Put skb_shared_info exactly at the end of allocated zone, + * to allow max possible filling before reallocation. + */ + size = SKB_WITH_OVERHEAD(ksize(data)); prefetchw(data + size); /* @@ -197,7 +206,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, * the tail pointer in struct sk_buff! */ memset(skb, 0, offsetof(struct sk_buff, tail)); - skb->truesize = size + sizeof(struct sk_buff); + /* Account for allocated memory : skb + skb->head */ + skb->truesize = SKB_TRUESIZE(size); atomic_set(&skb->users, 1); skb->head = data; skb->data = data; diff --git a/net/core/sock.c b/net/core/sock.c index 83c462d3f451..5a087626bb3a 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -207,7 +207,7 @@ static struct lock_class_key af_callback_keys[AF_MAX]; * not depend upon such differences. */ #define _SK_MEM_PACKETS 256 -#define _SK_MEM_OVERHEAD (sizeof(struct sk_buff) + 256) +#define _SK_MEM_OVERHEAD SKB_TRUESIZE(256) #define SK_WMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) #define SK_RMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) |