From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 2/3] skb: Drop "fastpath" variable for skb_cloned check in pskb_expand_head Date: Sat, 05 May 2012 07:37:24 +0200 Message-ID: <1336196244.3752.484.camel@edumazet-glaptop> References: <20120505001059.21292.31647.stgit@gitlad.jf.intel.com> <20120505002651.21292.19680.stgit@gitlad.jf.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, davem@davemloft.net, jeffrey.t.kirsher@intel.com To: Alexander Duyck Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:57228 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373Ab2EEFh2 (ORCPT ); Sat, 5 May 2012 01:37:28 -0400 Received: by wibhr7 with SMTP id hr7so1950257wib.1 for ; Fri, 04 May 2012 22:37:27 -0700 (PDT) In-Reply-To: <20120505002651.21292.19680.stgit@gitlad.jf.intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2012-05-04 at 17:26 -0700, Alexander Duyck wrote: > Since there is now only one spot that actually uses "fastpath" there isn't > much point in carrying it. Instead we can just use a check for skb_cloned > to verify if we can perform the fast-path free for the head or not. > > Signed-off-by: Alexander Duyck > --- > > net/core/skbuff.c | 22 ++++++++-------------- > 1 files changed, 8 insertions(+), 14 deletions(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 4d085d4..17e4b1e 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -932,7 +932,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > u8 *data; > int size = nhead + (skb_end_pointer(skb) - skb->head) + ntail; > long off; > - bool fastpath; > > BUG_ON(nhead < 0); > > @@ -941,16 +940,6 @@ 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; > - } > - > data = kmalloc(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), > gfp_mask); > if (!data) > @@ -966,9 +955,12 @@ 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])); > > - if (fastpath) { > - skb_free_head(skb); > - } else { > + /* > + * if shinfo is shared we must drop the old head gracefully, but if it > + * is not we can just drop the old head and let the existing refcount > + * be since all we did is relocate the values > + */ > + if (skb_cloned(skb)) { > /* copy this zero copy skb frags */ > if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) { > if (skb_copy_ubufs(skb, gfp_mask)) > @@ -981,6 +973,8 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, > skb_clone_fraglist(skb); > > skb_release_data(skb); > + } else { > + skb_free_head(skb); > } > off = (data + nhead) - skb->head; > > Excellent Acked-by: Eric Dumazet