Re: [PATCH net-next resubmit] skbuff: optimize the pull_pages code in __pskb_pull_tail()
From: Eric Dumazet <hidden>
Date: 2017-07-17 07:32:44
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Mon, 2017-07-17 at 10:22 +0800, Lin Zhang wrote:
quoted hunk ↗ jump to hunk
In the pull_pages code block, if the first frag size > eat, we can end the loop in advance to avoid extra copy. Signed-off-by: Lin Zhang <redacted> --- net/core/skbuff.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/net/core/skbuff.c b/net/core/skbuff.c index f990eb8..c00a1df 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c@@ -1720,6 +1720,10 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta) skb_shinfo(skb)->frags[k].page_offset += eat; skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat); eat = 0; + if (!i) { + k = skb_shinfo(skb)->nr_frags; + break; + } } k++; }
-CC lkml (no need to spam lkml for netdev patches ) Why even reading skb_shinfo(skb)->nr_frags to write it again ? I would use something like :
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8b11341ed69ad97d34dd3e9b73c8c44ef7c452ff..a562b0e61afa3faf7abdd7f9209ae9096310fb7d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c@@ -1719,13 +1719,15 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta) if (eat) { skb_shinfo(skb)->frags[k].page_offset += eat; skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat); + if (!i) + goto end; eat = 0; } k++; } } skb_shinfo(skb)->nr_frags = k; - +end: skb->tail += delta; skb->data_len -= delta;