From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Luis R. Rodriguez" Subject: Re: Stop using tasklets for bottom halves Date: Mon, 7 Sep 2009 21:16:38 -0700 Message-ID: <43e72e890909072116v33ecafc4ma7f5a68825f14e9@mail.gmail.com> References: <43e72e890909071558s637b45c7i10807587dc40e8c4@mail.gmail.com> <20090907171406.6a4b6116@nehalam> <1252376254.21261.2052.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Stephen Hemminger , Ingo Molnar , Michael Buesch , "John W. Linville" , linux-wireless , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matt Smith , Kevin Hayes , Bob Copeland , Jouni Malinen , Ivan Seskar , ic.felix-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org To: rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org Return-path: In-Reply-To: <1252376254.21261.2052.camel-f9ZlEuEWxVcI6MkJdU+c8EEOCMrvLtNR@public.gmane.org> Sender: linux-wireless-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On Mon, Sep 7, 2009 at 7:17 PM, Steven Rostedt wro= te: > On Mon, 2009-09-07 at 17:14 -0700, Stephen Hemminger wrote: >> On Mon, 7 Sep 2009 15:58:50 -0700 >> "Luis R. Rodriguez" wrote: >> >> > A while ago I had read about an effort to consider removing taskle= ts >> > [1] or at least trying to not use them. I'm unaware of the progres= s in >> > this respect but since reading that article have always tried to >> > evaluate whether or not we need tasklets on wireless drivers. I ha= ve >> > also wondered whether work in irq context in other parts of the ke= rnel >> > can be moved to process context, a curious example being timers. I= 'll >> > personally be trying to using only process context on bottom halve= s on >> > future drivers but I figured it may be a good time to ask how seri= ous >> > 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 i= s a >> > good step forward to take? Has anyone made tests or changes on a >> > specific driver from irq context to process context and proven the= re >> > are no significant advantages of using irq context where you would >> > have expected it? >> > >> > Wireless in particular should IMHO not require taskets for anythin= g >> > time sensitive that I can think about except perhaps changing chan= nels >> > quickly and to do that appropriately also process pending RX frame= s >> > prior to a switch. It remains to be seen experimentally whether or= not >> > using a workqueue for RX processing would affect the time to switc= h >> > 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 a= ny >> > 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/ >> > >> > =C2=A0 Luis >> > -- >> > To unsubscribe from this list: send the line "unsubscribe netdev" = in >> > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info= =2Ehtml >> >> 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 tha= t 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. What day in specific was this planned for at Plumbers? Luis -- To unsubscribe from this list: send the line "unsubscribe linux-wireles= s" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html