Date: Tue, 11 Dec 2012 15:15:26 +0100 From: =?ISO-8859-1?Q?Ermal_Lu=E7i?= <eri@freebsd.org> To: Barney Cordoba <barney_cordoba@yahoo.com> Cc: freebsd-net <freebsd-net@freebsd.org>, "Clement Hermann \(nodens\)" <nodens2099@gmail.com>, Jack Vogel <jfvogel@gmail.com> Subject: Re: igb and ALTQ in 9.1-rc3 Message-ID: <CAPBZQG030sSLT__b4cYA2e07t-77pvv9S3f8HnZfYpsXKEqTkQ@mail.gmail.com> In-Reply-To: <1355231140.51621.YahooMailClassic@web121603.mail.ne1.yahoo.com> References: <20121211075853.GU48639@FreeBSD.org> <1355231140.51621.YahooMailClassic@web121603.mail.ne1.yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Dec 11, 2012 at 2:05 PM, Barney Cordoba <barney_cordoba@yahoo.com>wrote: > > > --- On Tue, 12/11/12, Gleb Smirnoff <glebius@FreeBSD.org> wrote: > > > From: Gleb Smirnoff <glebius@FreeBSD.org> > > Subject: Re: igb and ALTQ in 9.1-rc3 > > To: "Jack Vogel" <jfvogel@gmail.com> > > Cc: "Clement Hermann (nodens)" <nodens2099@gmail.com>, "Barney Cordoba" > <barney_cordoba@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-unsubscribe@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. -- Ermal
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAPBZQG030sSLT__b4cYA2e07t-77pvv9S3f8HnZfYpsXKEqTkQ>