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

Gurucharan Shetty shettyg at nicira.com
Thu Jul 11 18:13:00 UTC 2013


On Thu, Jul 11, 2013 at 10:43 AM, Ben Pfaff <blp at nicira.com> wrote:

> 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.
>
Sounds good. I applied it and pushed this series to master and 1.11.
Thanks for the reviews.
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