[ovs-dev] [PATCH 3/3] [bug 2462] datapath: Increase maximum number of datapath ports.

Pravin Shelar pshelar at nicira.com
Tue Feb 7 09:54:18 UTC 2012


On Mon, Feb 6, 2012 at 9:45 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Mon, Feb 06, 2012 at 08:56:02PM -0800, Jesse Gross wrote:
>> OVS userspace tries not to recycle port numbers, which means that even
>> for a constant number of VMs on a machine if there is some churn
>> (maybe from migrations) over time we'll keep on expanding the table
>> and allocating more memory that's not really used.
>
> Right.  If I'm following this conversation correctly (I haven't read the
> patches) then the kernel datapath is switching to using a strategy where
> the space required for the port array is O(max_port) where max_port is
> the highest-numbered port in use, regardless of the number of ports
> actually in use.  Is that right?  If it is, it worries me a little,
> since it makes it expensive to use sparse port numbers.  Why not a hash
> (or a radix tree, or whatever) of the port number?
>

Radix tree is good idea, it is already using RCU. I need to check
compatibility with older kernel for RCU access for radix tree.

--Pravin.



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