From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [net-next RFC] pktgen: don't wait for the device who doesn't free skb immediately after sent Date: Wed, 28 Nov 2012 14:48:52 +0800 Message-ID: <50B5B3D4.1070106@redhat.com> References: <1353916612-6357-1-git-send-email-jasowang@redhat.com> <20121126093728.0a10f97f@nehalam.linuxnetplumber.net> <50B46179.4040809@redhat.com> <20121127084919.1587c647@nehalam.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Cc: mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, davem@davemloft.net To: Stephen Hemminger Return-path: In-Reply-To: <20121127084919.1587c647@nehalam.linuxnetplumber.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On 11/28/2012 12:49 AM, Stephen Hemminger wrote: > On Tue, 27 Nov 2012 14:45:13 +0800 > Jason Wang wrote: > >> On 11/27/2012 01:37 AM, Stephen Hemminger wrote: >>> On Mon, 26 Nov 2012 15:56:52 +0800 >>> Jason Wang wrote: >>> >>>> Some deivces do not free the old tx skbs immediately after it has been sent >>>> (usually in tx interrupt). One such example is virtio-net which optimizes for >>>> virt and only free the possible old tx skbs during the next packet sending. This >>>> would lead the pktgen to wait forever in the refcount of the skb if no other >>>> pakcet will be sent afterwards. >>>> >>>> Solving this issue by introducing a new flag IFF_TX_SKB_FREE_DELAY which could >>>> notify the pktgen that the device does not free skb immediately after it has >>>> been sent and let it not to wait for the refcount to be one. >>>> >>>> Signed-off-by: Jason Wang >>> Another alternative would be using skb_orphan() and skb->destructor. >>> There are other cases where skb's are not freed right away. >>> -- >>> To unsubscribe from this list: send the line "unsubscribe netdev" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Hi Stephen: >> >> Do you mean registering a skb->destructor for pktgen then set and check >> bits in skb->tx_flag? > Yes. Register a destructor that does something like update a counter (number of packets pending), > then just spin while number of packets pending is over threshold. > -- Not sure this is the best method, since pktgen was used to test the tx process of the device driver and NIC. If we use skb_orhpan(), we would miss the test of tx completion part.