Re: [Qemu-devel] [PATCH V2 1/3] colo-compare: introduce colo compare initlization

[Li Zhijian]

On 04/01/2016 01:11 PM, Jason Wang wrote:
> On 03/31/2016 05:24 PM, Dr. David Alan Gilbert wrote:
> > * Zhang Chen (address@hidden) wrote:
> > > On 03/30/2016 05:25 PM, Dr. David Alan Gilbert wrote:
> > > > * Zhang Chen (address@hidden) wrote:
> > > > > packet come from primary char indev will be send to
> > > > > outdev - packet come from secondary char dev will be drop
> > > > Please put in the description an example of how you invoke
> > > > the filter on the primary and secondary.
> > > OK.
> > > colo-compare get packet from chardev(primary_in,secondary_in),
> > > and output to other chardev(outdev), so, we can use it with the
> > > help of filter-mirror and filter-redirector. like that:
> > Wow, this is a bit more complicated than I expected - I was expecting just one
> > socket.  So let me draw this out; see comments below.
> >
> > > primary:
> > > -netdev
> > > tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
> > > -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
> > > -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
> > > -chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
> > > -chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
> > > -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
> > > -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
> > > -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
> > > -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
> > > -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
> > > -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
> > > -object 
> > > colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0
> >              ----> mirror0: socket:secondary:9003
> >              |
> >          mirror-m0     <-- e1000
> >              |
> >              v
> >          redirector-redire1 ---> compare0 socket:primary:9001 (to compare0-0)
> >
> >              -----< compare0-0 socket:primary:9001 (to compare0)
> >              |  primary_in
> >              |
> >          compare-comp0       -----> compare_out0 socket:primary:9005
> >              |
> >              |  secondary_in
> >              -----< compare1   socket:secondary:9004
> >
> > tap <-- redirector-redire0 <--- compare_out socket:primary:9005 (from 
> > compare_out0)
> >
> >
> > > secondary:
> > > -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down
> > > script=/etc/qemu-ifdown
> > > -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
> > > -chardev socket,id=red0,host=3.3.3.3,port=9003
> > > -chardev socket,id=red1,host=3.3.3.3,port=9004
> > > -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
> > > -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
> >              ----> red0 socket::9003
> >              |
> > tap <-- redirector-f1 <--
> >                             e1000
> >      --> redirector-f2 -->
> >              |
> >              ----< red1 socket::9004
> >
> > OK, so I think we need to find a way to fix two things:
> >     a) There must be an easier way of connecting two filters within the same
> >        qemu than going up to the kernel's socket code, around it's TCP stack
> >        and back.  Is there a better type of chardev to use we can short circuit
> >        with - it shouldn't need to leave QEMU (although I can see it's easier
> >        for debugging like this).  Jason/Dan - any ideas?
>
> Looks like there's no such type of chardev. I think we could start with
> tcp socket chardev first and do necessary optimization on top. In fact,
> there's also advantages, with tcp sockets, the colo-compare codes could
> even be an independent program out of qemu.
>
> For the chardev type, this also reminds me one thing. Since
> mirror/redirector can only work for tcp socket, we may need inspect the
> chardev types and fail if not a tcp socket like what vhost-user did.
>
>
> >     b) We should only need one socket for the connection between primary and
> >        secondary - I'm not sure how to change it to let it do that.
>
> Looks like we can (e.g for secondary):
>
> -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
> -chardev socket,id=red0,host=3.3.3.3,port=9003
> -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
> -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red0
>
> If not, probably a bug.

Right,
but firstly, 'chardev socket' need to enable 'mux=on' if we want two filter 
reference the
same socket.

Thanks

> >     c) You need to be able to turn off nagling (socket no delay) on the sockets;
> >       I found a noticeable benefit of doing this on the connection between 
> > primary
> >       and secondary in my world.
>
> Right.
>
> > Dave
>
>
>
>
> .