[ovs-dev] [docs 2/3] ovs-vswitchd: Document some limits.

[Ethan Jackson]

Looks good, thanks.

Ethan

On Mon, May 14, 2012 at 11:18 AM, Ben Pfaff <blp at nicira.com> wrote:
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  vswitchd/ovs-vswitchd.8.in |   43 +++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/vswitchd/ovs-vswitchd.8.in b/vswitchd/ovs-vswitchd.8.in
> index 6c9f3e4..bfd70fb 100644
> --- a/vswitchd/ovs-vswitchd.8.in
> +++ b/vswitchd/ovs-vswitchd.8.in
> @@ -207,6 +207,49 @@ enabled.
>  .so ofproto/ofproto-unixctl.man
>  .so lib/vlog-unixctl.man
>  .so lib/stress-unixctl.man
> +.
> +.SH "LIMITS"
> +.
> +.PP
> +We believe these limits to be accurate as of this writing.  These
> +limits assume the use of the Linux kernel datapath.
> +.
> +.IP \(bu
> +Approximately 256 bridges given the allowance of 5,000 file
> +descriptors that \fBovs\-ctl\fR(8) configures.  (\fBovs\-vswitchd\fR
> +requires 17 file descriptors per datapath.)
> +.
> +.IP \(bu
> +65,280 ports per bridge.  Performance will degrade beyond 1,024 ports
> +per bridge due to fixed hash table sizing.
> +.
> +.IP \(bu
> +2,048 MAC learning entries per bridge.
> +.
> +.IP \(bu
> +Kernel flows are limited only by memory available to the kernel.
> +Performance will degrade beyond 1,048,576 kernel flows per bridge with
> +a 32-bit kernel, beyond 262,144 with a 64-bit kernel.
> +(\fBovs\-vswitchd\fR should never install anywhere near that many
> +flows.)
> +.
> +.IP \(bu
> +OpenFlow flows are limited only by available memory.  Performance is
> +linear in the number of unique wildcard patterns.  That is, an
> +OpenFlow table that contains many flows that all match on the same
> +fields in the same way has a constant-time lookup, but a table that
> +contains many flows that match on different fields requires lookup
> +time linear in the number of flows.
> +.
> +.IP \(bu
> +255 ports per bridge participating in 802.1D Spanning Tree Protocol.
> +.
> +.IP \(bu
> +32 mirrors per bridge.
> +.
> +.IP \(bu
> +15 bytes for the name of a port.  (This is a Linux kernel limitation.)
> +.
>  .SH "SEE ALSO"
>  .BR ovs\-appctl (8),
>  .BR ovs\-brcompatd (8),
> --
> 1.7.2.5
>
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