[ovs-dev] [PATCH 1/2] ovs-vswitchd: Correct the documentation on the limits for bridges and ports.

Ben Pfaff blp at nicira.com
Thu Jul 11 17:43:58 UTC 2013


On Thu, Jul 11, 2013 at 10:39:38AM -0700, Gurucharan Shetty wrote:
> On Thu, Jul 11, 2013 at 10:34 AM, Gurucharan Shetty <shettyg at nicira.com>wrote:
> 
> > On Thu, Jul 11, 2013 at 10:22 AM, Ben Pfaff <blp at nicira.com> wrote:
> >
> >> On Thu, Jul 11, 2013 at 09:37:45AM -0700, Gurucharan Shetty wrote:
> >> > Signed-off-by: Gurucharan Shetty <gshetty at nicira.com>
> >>
> >> I'm not sure it's worth mentioning the 65,280 port limit, because it's
> >> about the same as the maximum number of file descriptors.
> >>
> >> At first thought, these limits seemed Linux specific, but I think that
> >> FreeBSD also needs a file descriptor per port (for a pcap handle), so
> >> maybe it's not worth saying that it is Linux specific.  The final note
> >> about performance beyond 1,024 ports is definitely specific to the
> >> Linux kernel datapath though.
> >>
> > Okay. How about the following wording?
> >
> > ovs-vswitchd started through ovs-ctl provides a limit of 5000 file
> > descriptors.  Creation of a single bridge consumes 3 file descriptors and
> > adding a port consumes 1 file descriptor.  The limits on the number of
> > bridges and ports is decided by the availability of file descriptors.  (For
> > Linux kernel datapath, performance will degrade beyond 1,024 ports per
> > bridge due to fixed hash table sizing.)
> >
> Or probably make the entire thing Linux specific.
> ovs-vswitchd started through ovs-ctl provides a limit of 5000 file
> descriptors. The limits on the number of bridges and ports is decided by
> the availability of file descriptors. On Linux, creation of a single bridge
> consumes 3 file descriptors and adding a port consumes 1 file descriptor.
> Performance will degrade beyond 1,024 ports per bridge due to fixed hash
> table sizing. Other platforms may have different limitations.

How about "With the Linux kernel datapath" instead of "On Linux",
because the netdev datapath has slightly different characteristics.
Otherwise I like this.



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