[ovs-dev] [PATCH 2/2] Raise MAC learning table capacity from 1, 024 to 2, 048 entries per bridge.

Ben Pfaff blp at nicira.com
Sun Sep 13 18:47:43 UTC 2009

Justin Pettit <jpettit at nicira.com> writes:

> On Sep 11, 2009, at 10:40 PM, Ben Pfaff wrote:
>> Given a possible 1,024 ports on a bridge the previous limit of 2,048
>> entries seems low.
> I believe that should read 1024, not 2048.

Yes thanks.

> Even 2048 entries seems kind of low to me.  Look around on the web, 8K
> entries seems pretty common in hardware switches.  A quick look in the
> kernel sources at the bridge seems to indicate they have no limit
> (which is worrying in its own right).

Our current implementation of MAC learning statically allocates
the entire MAC-learning table at a cost of about 40 kB per table.
Doubling the number of entries to 2,048 makes them more like 80
kB.  I'm nervous about increasing the limit to 8,192 which would
make the cost 320 kB each.  Hence the comment about wanting to
switch to dynamic memory allocation if we raise the limit any

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