On Thu, Apr 19, 2012 at 11:06:38PM +0200, K. Macy wrote:
> On Thu, Apr 19, 2012 at 11:22 PM, Luigi Rizzo <ri...@iet.unipi.it> wrote:
> > On Thu, Apr 19, 2012 at 10:34:45PM +0200, K. Macy wrote:
> >> >> This is indeed a big problem. ?I'm working (rough edges remain) on
> >> >> changing the routing table locking to an rmlock (read-mostly) which
> >> >
> >>
> >> This only helps if your flows aren't hitting the same rtentry.
> >> Otherwise you still convoy on the lock for the rtentry itself to
> >> increment and decrement the rtentry's reference count.
> >>
> >> > i was wondering, is there a way (and/or any advantage) to use the
> >> > fastforward code to look up the route for locally sourced packets ?
> >
> > actually, now that i look at the code, both ip_output() and
> > the ip_fastforward code use the same in_rtalloc_ign(...)
> >
> >> >
> >>
> >> If the number of peers is bounded then you can use the flowtable. Max
> >> PPS is much higher bypassing routing lookup. However, it doesn't scale
> >> to arbitrary flow numbers.
> >
> > re. flowtable, could you point me to what i should do instead of
> > calling in_rtalloc_ign() ?
>
> If you build with it in your kernel config and enable the sysctl
> ip_output will automatically use it for TCP and UDP connections. If
> you're doing forwarding you'll need to patch the forwarding path.
cool.
For the records, with "netsend 10.0.0.2 ports 18 0 5" on an ixgbe
talking to a remote host i get the following results (with a single
port netsend does a connect() and then send(), otherwise it
loops around a sendto() )
net.flowtable.enabled port ns/pkt
-----------------------------------------------------
not compiled in 5000 944 M_FLOWID not set
0 (disable) 5000 1004
1 (enable) 5000 980
not compiled in 5000-5001 3400 M_FLOWID not set
0 (disable) 5000-5001 1418
1 (enable) 5000-5001 1230
The small penalty when flowtable is disabled but compiled in is
probably because the net.flowtable.enable flag is checked
a bit deep in the code.
The advantage with non-connect()ed sockets is huge. I don't
quite understand why disabling the flowtable still helps there.
cheers
luigi
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