From: Ian Campbell <Ian.Campbell@citrix•com>
To: "Michael S. Tsirkin" <mst@redhat•com>
Cc: David Miller <davem@davemloft•net>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"eric.dumazet@gmail•com" <eric.dumazet@gmail•com>
Subject: Re: [PATCH RFC 1/6] skbuff: support per-page destructors in copy_ubufs
Date: Sat, 12 May 2012 07:01:24 +0100 [thread overview]
Message-ID: <1336802484.3891.24.camel@dagon.hellion.org.uk> (raw)
In-Reply-To: <20120511163057.GB10344@redhat.com>
On Fri, 2012-05-11 at 17:30 +0100, Michael S. Tsirkin wrote:
> On Fri, May 11, 2012 at 03:08:36PM +0300, Michael S. Tsirkin wrote:
> > On Fri, May 11, 2012 at 11:58:12AM +0100, Ian Campbell wrote:
> > > On Fri, 2012-05-11 at 10:00 +0100, Ian Campbell wrote:
> > > > I'm seeing copy_ubufs called in my remote NFS test, which I don't
> > > > think I expected -- I'll investigate why this is happening today.
> > >
> > > It's tcp_transmit_skb which can (conditionally) call skb_clone
> > > (backtrace below)
> >
> > Interesting. I didn't realise we clone skbs on data path:
> > tcp_write_xmit calls tcp_transmit_skb with clone_it flag.
> > Could someone comment on why we need to clone on good path
> > like this?
>
> Hmm, it's in case we need to retransmit it later.
I wonder if we could avoid the copy_ubuf in this particular clone path
and have any subsequent calls to copy_ubufs use skb->fclone to determine
if it can safely replace the frags?
If it cannot then could it do a full copy of the skb (including new
shinfo, new frag pages etc) as a fallback?
Ian.
next prev parent reply other threads:[~2012-05-12 6:01 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-07 13:53 [PATCH RFC 0/6] copy aside frags with destructors (was [PATCH 7/9] net: add skb_orphan_frags to copy aside frags with destructors) Michael S. Tsirkin
2012-05-07 13:54 ` [PATCH RFC 1/6] skbuff: support per-page destructors in copy_ubufs Michael S. Tsirkin
2012-05-10 17:46 ` Ian Campbell
2012-05-10 18:42 ` Michael S. Tsirkin
2012-05-11 9:00 ` Ian Campbell
2012-05-11 10:58 ` Ian Campbell
2012-05-11 12:08 ` Michael S. Tsirkin
2012-05-11 16:30 ` Michael S. Tsirkin
2012-05-12 6:01 ` Ian Campbell [this message]
2012-05-13 10:10 ` Michael S. Tsirkin
2012-05-11 21:12 ` David Miller
2012-05-07 13:54 ` [PATCH RFC 2/6] skbuff: add an api to orphan frags Michael S. Tsirkin
2012-05-08 12:47 ` Michael S. Tsirkin
2012-05-07 13:54 ` [PATCH RFC 3/6] skbuff: convert to skb_orphan_frags Michael S. Tsirkin
2012-05-07 13:54 ` [PATCH RFC 4/6] tun: orphan frags on xmit Michael S. Tsirkin
2012-05-08 14:36 ` Michael S. Tsirkin
2012-05-07 13:54 ` [PATCH RFC 5/6] net: orphan frags on receive Michael S. Tsirkin
2012-05-09 13:54 ` Ian Campbell
2012-05-09 15:12 ` Michael S. Tsirkin
2012-05-14 19:18 ` Michael S. Tsirkin
2012-05-07 13:54 ` [PATCH RFC 6/6] skbuff: set zerocopy flag on frag destructor Michael S. Tsirkin
2012-05-08 12:46 ` Michael S. Tsirkin
2012-05-08 9:41 ` [PATCH RFC 0/6] copy aside frags with destructors (was [PATCH 7/9] net: add skb_orphan_frags to copy aside frags with destructors) Michael S. Tsirkin
2012-05-08 10:54 ` Ian Campbell
2012-05-08 14:49 ` Michael S. Tsirkin
2012-05-09 13:18 ` Ian Campbell
2012-05-09 13:52 ` Michael S. Tsirkin
2012-05-09 14:01 ` Ian Campbell
2012-05-09 15:27 ` Michael S. Tsirkin
2012-05-09 14:56 ` Michael S. Tsirkin
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