* [PATCH v3] net: don't reallocate skb->head unless the current one hasn't the needed extra size or is shared
@ 2010-11-30 8:48 Changli Gao
2010-12-03 17:47 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Changli Gao @ 2010-11-30 8:48 UTC (permalink / raw)
To: David S. Miller; +Cc: netdev, Changli Gao, Eric Dumazet
skb head being allocated by kmalloc(), it might be larger than what
actually requested because of discrete kmem caches sizes. Before
reallocating a new skb head, check if the current one has the needed
extra size.
Do this check only if skb head is not shared.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
V3: update the comment.
v2: apply this trick for the cloned but not shared skb
net/core/skbuff.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 104f844..8814a9a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -778,6 +778,28 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
size = SKB_DATA_ALIGN(size);
+ /* Check if we can avoid taking references on fragments if we own
+ * the last reference on skb->head. (see skb_release_data())
+ */
+ if (!skb->cloned)
+ fastpath = true;
+ else {
+ int delta = skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1;
+
+ fastpath = atomic_read(&skb_shinfo(skb)->dataref) == delta;
+ }
+
+ if (fastpath &&
+ size + sizeof(struct skb_shared_info) <= ksize(skb->head)) {
+ memmove(skb->head + size, skb_shinfo(skb),
+ offsetof(struct skb_shared_info,
+ frags[skb_shinfo(skb)->nr_frags]));
+ memmove(skb->head + nhead, skb->head,
+ skb_tail_pointer(skb) - skb->head);
+ off = nhead;
+ goto adjust_others;
+ }
+
data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask);
if (!data)
goto nodata;
@@ -791,17 +813,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
skb_shinfo(skb),
offsetof(struct skb_shared_info, frags[skb_shinfo(skb)->nr_frags]));
- /* Check if we can avoid taking references on fragments if we own
- * the last reference on skb->head. (see skb_release_data())
- */
- if (!skb->cloned)
- fastpath = true;
- else {
- int delta = skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1;
-
- fastpath = atomic_read(&skb_shinfo(skb)->dataref) == delta;
- }
-
if (fastpath) {
kfree(skb->head);
} else {
@@ -816,6 +827,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
off = (data + nhead) - skb->head;
skb->head = data;
+adjust_others:
skb->data += off;
#ifdef NET_SKBUFF_DATA_USES_OFFSET
skb->end = size;
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] net: don't reallocate skb->head unless the current one hasn't the needed extra size or is shared
2010-11-30 8:48 [PATCH v3] net: don't reallocate skb->head unless the current one hasn't the needed extra size or is shared Changli Gao
@ 2010-12-03 17:47 ` David Miller
2010-12-03 18:01 ` Eric Dumazet
0 siblings, 1 reply; 3+ messages in thread
From: David Miller @ 2010-12-03 17:47 UTC (permalink / raw)
To: xiaosuo; +Cc: netdev, eric.dumazet
From: Changli Gao <xiaosuo@gmail.com>
Date: Tue, 30 Nov 2010 16:48:46 +0800
> skb head being allocated by kmalloc(), it might be larger than what
> actually requested because of discrete kmem caches sizes. Before
> reallocating a new skb head, check if the current one has the needed
> extra size.
>
> Do this check only if skb head is not shared.
>
> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
Eric, ACK?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] net: don't reallocate skb->head unless the current one hasn't the needed extra size or is shared
2010-12-03 17:47 ` David Miller
@ 2010-12-03 18:01 ` Eric Dumazet
0 siblings, 0 replies; 3+ messages in thread
From: Eric Dumazet @ 2010-12-03 18:01 UTC (permalink / raw)
To: David Miller; +Cc: xiaosuo, netdev
Le vendredi 03 décembre 2010 à 09:47 -0800, David Miller a écrit :
> From: Changli Gao <xiaosuo@gmail.com>
> Date: Tue, 30 Nov 2010 16:48:46 +0800
>
> > skb head being allocated by kmalloc(), it might be larger than what
> > actually requested because of discrete kmem caches sizes. Before
> > reallocating a new skb head, check if the current one has the needed
> > extra size.
> >
> > Do this check only if skb head is not shared.
> >
> > Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> > Cc: Eric Dumazet <eric.dumazet@gmail.com>
>
> Eric, ACK?
Yes :)
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Thanks !
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2010-12-03 18:01 UTC | newest]
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2010-11-30 8:48 [PATCH v3] net: don't reallocate skb->head unless the current one hasn't the needed extra size or is shared Changli Gao
2010-12-03 17:47 ` David Miller
2010-12-03 18:01 ` Eric Dumazet
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