>-----Original Message----- >From: Eric Dumazet [mailto:eric.dumazet@xxxxxxxxx] >Sent: Saturday, June 05, 2010 10:56 PM >To: Xin, Xiaohui >Cc: netdev@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >mst@xxxxxxxxxx; mingo@xxxxxxx; davem@xxxxxxxxxxxxx; herbert@xxxxxxxxxxxxxxxxxxx; >jdike@xxxxxxxxxxxxxxx >Subject: Re: [RFC PATCH v7 11/19] Use callback to deal with skb_release_data() specially. > >Le samedi 05 juin 2010 à 18:14 +0800, xiaohui.xin@xxxxxxxxx a écrit : >> From: Xin Xiaohui <xiaohui.xin@xxxxxxxxx> >> >> If buffer is external, then use the callback to destruct >> buffers. >> >> Signed-off-by: Xin Xiaohui <xiaohui.xin@xxxxxxxxx> >> Signed-off-by: Zhao Yu <yzhao81new@xxxxxxxxx> >> Reviewed-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx> >> --- >> net/core/skbuff.c | 11 +++++++++++ >> 1 files changed, 11 insertions(+), 0 deletions(-) >> >> diff --git a/net/core/skbuff.c b/net/core/skbuff.c >> index 37587f0..418457c 100644 >> --- a/net/core/skbuff.c >> +++ b/net/core/skbuff.c >> @@ -385,6 +385,11 @@ static void skb_clone_fraglist(struct sk_buff *skb) >> >> static void skb_release_data(struct sk_buff *skb) >> { >> + /* check if the skb has external buffers, we have use destructor_arg >> + * here to indicate >> + */ >> + struct skb_external_page *ext_page = skb_shinfo(skb)->destructor_arg; >> + > >Oh well. This is v7 of your series, and nobody complained yet ? > >This is a new cache miss on a _critical_ path. Ok, I would remove the declaration here to avoid the new cache miss. > > >> if (!skb->cloned || >> !atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1, >> &skb_shinfo(skb)->dataref)) { >> @@ -397,6 +402,12 @@ static void skb_release_data(struct sk_buff *skb) >> if (skb_has_frags(skb)) >> skb_drop_fraglist(skb); >> >> + /* if the skb has external buffers, use destructor here, >> + * since after that skb->head will be kfree, in case skb->head >> + * from external buffer cannot use kfree to destroy. >> + */ > >Why not deferring here the access to skb_shinfo(skb)->destructor_arg ? And references skb_shinfo(skb)->destructor_arg here. > >> + if (dev_is_mpassthru(skb->dev) && ext_page && ext_page->dtor) >> + ext_page->dtor(ext_page); >> kfree(skb->head); >> } >> } > >if (dev_is_mpassthru(skb->dev)) { > struct skb_external_page *ext_page = > skb_shinfo(skb)->destructor_arg; > if (ext_page && ext_page->dtor) > ext_page->dtor(ext_page); >} > >destructor_arg should me moved before frags[] if you really want to use it. Thanks for the patch. But why destructor_arg before frags[] is better than after frags[]? skb_release_data() will reference both of them........ > >diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h >index bf243fc..b136d90 100644 >--- a/include/linux/skbuff.h >+++ b/include/linux/skbuff.h >@@ -202,10 +202,11 @@ struct skb_shared_info { > */ > atomic_t dataref; > >- skb_frag_t frags[MAX_SKB_FRAGS]; > /* Intermediate layers must ensure that destructor_arg > * remains valid until skb destructor */ > void * destructor_arg; >+ >+ skb_frag_t frags[MAX_SKB_FRAGS]; > }; > > /* We divide dataref into two halves. The higher 16 bits hold references > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
