From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH V7 2/4 net-next] skbuff: Add userspace zero-copy buffers in skb Date: Tue, 28 Jun 2011 16:35:08 -0700 (PDT) Message-ID: <20110628.163508.222352070705159851.davem@davemloft.net> References: <1309189510.21764.1.camel@localhost.localdomain> <20110627.155426.51839633424542723.davem@davemloft.net> <1309279892.3559.6.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: mst@redhat.com, eric.dumazet@gmail.com, avi@redhat.com, arnd@arndb.de, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: mashirle@us.ibm.com Return-path: In-Reply-To: <1309279892.3559.6.camel@localhost.localdomain> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Shirley Ma Date: Tue, 28 Jun 2011 09:51:32 -0700 > On Mon, 2011-06-27 at 15:54 -0700, David Miller wrote: >> From: Shirley Ma >> Date: Mon, 27 Jun 2011 08:45:10 -0700 >> >> > To support skb zero-copy, a pointer is needed to add to skb share >> info. >> > Do you agree with this approach? If not, do you have any other >> > suggestions? >> >> I really can't form an opinion unless I am shown the complete >> implementation, what this give us in return, what the impact is, etc. .. > You can see the overall CPU saved 50% w/i zero-copy. > > The impact is every skb allocation consumed one more pointer in skb > share info, and a pointer check in skb release when last reference is > gone. > > For skb clone, skb expand private head and skb copy, it still keeps copy > the buffers to kernel, so we can avoid user application, like tcpdump to > hold the user-space buffers too long. Ok, now show me the "complete implementation". I'm as interested in the code as I am in the numbers, that's why I asked for both.