On Wed, Jan 17, 2001 at 06:22:41PM +0100, Gleb Natapov wrote:
> On Wed, Jan 17, 2001 at 05:14:38PM +0100, Andi Kleen wrote:
> > On Wed, Jan 17, 2001 at 02:51:48PM +0100, Gleb Natapov wrote:
> > >
> > > You are trying to say that if I'll connect to my router via 9600 serial
> > > line and run 'ip monitor'
> > > there the routing daemon will not be able to feed routes to the kernel
> > > quicker than ip monitor will
> > > be able to read them and send output via slow serial line?! Somehow 9600
> > > serial line become a
> > > bottleneck! Are you sure about that, or I misunderstood you?
> > You misunderstood me. The kernel side doesn't do any flow control, it just
> > drops messages when the
> > buffers fill up. The user side does flow control by blocking or EAGAIN,
> > e.g. you submitting new
> > routes.
> What user side? There are to sides: W - feeds routes to the kernel, R - read
> netlink updates from the kernel.
(W) is flow controlled.
(R) is in a sense flow controlled too because it can only get information
the kernel queues, but the kernel cheats a bit by dropping stuff when the
> Who does flow control and how?
> W knows nothing about R it simple adds routes to the kernel with the speed
> kernel can process them.
Which is the flow control -- it gets blocked when the kernel cannot keep up.