On Mon, 07 Sep 2009 22:17:34 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > On Mon, 2009-09-07 at 17:14 -0700, Stephen Hemminger wrote: > > On Mon, 7 Sep 2009 15:58:50 -0700 > > "Luis R. Rodriguez" <mcgrof@xxxxxxxxx> wrote: > > > > > A while ago I had read about an effort to consider removing tasklets > > > [1] or at least trying to not use them. I'm unaware of the progress in > > > this respect but since reading that article have always tried to > > > evaluate whether or not we need tasklets on wireless drivers. I have > > > also wondered whether work in irq context in other parts of the kernel > > > can be moved to process context, a curious example being timers. I'll > > > personally be trying to using only process context on bottom halves on > > > future drivers but I figured it may be a good time to ask how serious > > > was avoiding tasklets or using wrappers in the future to avoid irq > > > context is or is it advised. Do we have a general agreement this is a > > > good step forward to take? Has anyone made tests or changes on a > > > specific driver from irq context to process context and proven there > > > are no significant advantages of using irq context where you would > > > have expected it? > > > > > > Wireless in particular should IMHO not require taskets for anything > > > time sensitive that I can think about except perhaps changing channels > > > quickly and to do that appropriately also process pending RX frames > > > prior to a switch. It remains to be seen experimentally whether or not > > > using a workqueue for RX processing would affect the time to switch > > > channels negatively but I doubt it would be significant. I hope to > > > test that with ath9k_htc. > > > > > > What about gigabit or 10 Gigabit Ethernet drivers ? Do they face any > > > challenges which would yet need to be proven would not face issues > > > when processing bottom halves in process context? > > > > > > [1] http://lwn.net/Articles/239633/ > > > > > > Luis > > > -- > > > To unsubscribe from this list: send the line "unsubscribe netdev" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > Why not use NAPI, which is soft irq? Almost all 1G and 10G drivers > > use NAPI. > > > > Process context is too slow. > > Well, I'm hoping to prove the opposite. I'm working on some stuff that I > plan to present at Linux Plumbers. I've been too distracted by other > things, but hopefully I'll have some good numbers to present by then. > > -- Steve > > A good performance test is changing the behaviour of loopback device and running lmbench. This checks overhead without the specter of real hardware. -- -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
