On Tue, 2014-03-25 at 18:05 +0100, Arnd Bergmann wrote: > On Tuesday 25 March 2014 10:00:30 Florian Fainelli wrote: > > 2014-03-25 1:12 GMT-07:00 Arnd Bergmann <arnd@xxxxxxxx>: > > > On Tuesday 25 March 2014 12:06:31 Zhangfei Gao wrote: > > >> Dear Arnd > > >> > > >> On Mon, Mar 24, 2014 at 11:18 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > >> > On Monday 24 March 2014 22:14:56 Zhangfei Gao wrote: > > >> > ... > > >> > I think you still need to find a solution to ensure that the tx reclaim is > > >> > called eventually through a method other than start_xmit. > > >> > > >> In the iperf stress test, if move reclaim to poll, there is some > > >> error, sometimes sending zero packets. > > >> While keep reclaim in the xmit to reclaim transmitted packets looks > > >> stable in the test, > > >> There TX_DESC_NUM desc can be used. > > > > > > What I meant is that you need a correct implementation, presumably > > > you added a bug when you moved the function to poll(), and also you > > > forgot to add a timer. > > > > Using a timer to ensure completion of TX packets is a trick that > > worked in the past, but now that the networking stack got smarter, > > this might artificially increase the processing time of packets in the > > transmit path, and this will defeat features like TCP small queues > > etc.. as could be seen with the mvneta driver [1]. The best way really > > is to rely on TX completion interrupts when those exist as they cannot > > lie about the hardware status (in theory) and they should provide the > > fastest way to complete TX packets. > > By as Zhangfei Gao pointed out, this hardware does not have a working > TX completion interrupt. Using timers to do this has always just been > a workaround for broken hardware IMHO. For this kind of drivers, calling skb_orphan() from ndo_start_xmit() is mandatory. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
