--- On Tue, 12/11/12, Karim Fodil-Lemelin <fodillemlinka...@gmail.com> wrote:
> From: Karim Fodil-Lemelin <fodillemlinka...@gmail.com> > Subject: Re: igb and ALTQ in 9.1-rc3 > To: freebsd-net@freebsd.org > Cc: nodens2...@gmail.com > Date: Tuesday, December 11, 2012, 9:56 AM > On 11/12/2012 9:15 AM, Ermal Luçi > wrote: > > On Tue, Dec 11, 2012 at 2:05 PM, Barney Cordoba > > <barney_cord...@yahoo.com>wrote: > > > >> > >> --- On Tue, 12/11/12, Gleb Smirnoff <gleb...@freebsd.org> > wrote: > >> > >>> From: Gleb Smirnoff <gleb...@freebsd.org> > >>> Subject: Re: igb and ALTQ in 9.1-rc3 > >>> To: "Jack Vogel" <jfvo...@gmail.com> > >>> Cc: "Clement Hermann (nodens)" <nodens2...@gmail.com>, > "Barney Cordoba" > >> <barney_cord...@yahoo.com>, > freebsd-net@FreeBSD.org > >>> Date: Tuesday, December 11, 2012, 2:58 AM > >>> On Mon, Dec 10, 2012 at 03:31:19PM > >>> -0800, Jack Vogel wrote: > >>> J> UH, maybe asking the owner of the driver > would help > >>> :) > >>> J> > >>> J> ... and no, I've never been aware of > doing anything to > >>> stop supporting altq > >>> J> so you wouldn't see any commits. If > there's something > >>> in the altq code or > >>> J> support (which I have nothing to do with) > that caused > >>> this no-one informed > >>> J> me. > >>> > >>> Switching from if_start to if_transmit > effectively disables > >>> ALTQ support. > >>> > >>> AFAIR, there is some magic implemented in other > drivers that > >>> makes them > >>> modern (that means using if_transmit), but > still capable to > >>> switch to queueing > >>> mode if SIOCADDALTQ was casted upon them. > >>> > >> It seems pretty difficult to say that something is > compatible with > >> something else if it hasn't been tested in a few > years. > >> > >> It seems to me that ATLQ is the one that should > handle if_transmit. > >> although it's a good argument for having a raw > "send" function in > >> drivers. Ethernet drivers don't need more than a > send() routing that > >> loads a packet into the ring. The decision on what > to do if you can't > >> queue a packet should be in the network > layer, if we must still call > >> things layers. > >> > >> "start" is a leftover from a day when you stuffed a > buffer and waited > >> for an interrupt to stuff in another. The whole > idea is antiquated. > >> > >> Imagine drivers that pull packets off of a card and > simply queue it; > >> and that you simply submit a packet to be queued > for transmit. Instead > >> of trying to find 35 programmers that understand > all of the lock BS, > >> you only need to have a couple. > >> > >> I always disable all of the gobbledegook like > checksum offloading. They > >> just muddy the water and have very little effect on > performance. A modern > >> cpu can do a checksum as fast as you can manage the > "capabilities" without > >> disrupting the processing path. > >> > >> With FreeBSD, every driver is an experience. Some > suck so bad that they > >> should come with a warning. The MSK driver is > completely useless, as > >> an example. > >> > >> > >> BC > >> _______________________________________________ > >> freebsd-net@freebsd.org > mailing list > >> http://lists.freebsd.org/mailman/listinfo/freebsd-net > >> To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org" > >> > > During implementation of if_transmit altq was not > considered at all. > > The default if_transmit provides some compatibility but > that is void since > > altq has not been converted to call if_transmit after > processing the mbuf. > > > > ALTQ can be adapted quite easily to if_transmit model > it just wasn't done > > at the time. > > With if_transmit model it can even be modularized and > not be a compile > > kernel option since the queue of the iface is > abstracted now. > > > > I have always wanted to do a diff but have not yet got > to it. > > The change is quite simple just provide an > altq_transmit default method and > > just hook into if_transmit model on the fly. > > You surely need to handle some iface events and enable > altq based on > > request but its is not a hard to implement. > > > > I will always have this in my TODO but not sure when i > can get to it. > > > The issue is not only that igb doesn't support if_transmit > or if_start > method but that ALTQ isn't multiqueue ready and still uses > the IFQ_LOCK > for all of its enqueue/dequeue operations. A simple drop in > of > if_transmit is bound to cause race conditions on any > multiqueue driver > with ALTQ. > > I do have a patch set for this on igb but its ugly and needs > more work > although it should get you going. Let me know if your > interested I will > clean it up and send it over. For more information on ALTQ > discussion > and igb please read this thread: > http://freebsd.1045724.n5.nabble.com/em-igb-if-transmit-drbr-and-ALTQ-td5760338.html > > Best regards, > > Karim. At minimum, the drivers should make multiqueue an option, at least until it works better than a single queue driver. Many MOBOs have igb nics on board and such a mainstream NIC shouldn't be strapped using experimental code that clearly isn't ready for prime time. BC _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
