[ovs-dev] [PATCH] ofproto: Remove per-flow miss hash table from upcall handler.

Ryan Wilson wryan at vmware.com
Fri May 9 21:38:33 UTC 2014


Hey Ben,

Sorry for the delayed response. Unfortunately, I've had some issues with setting up an NVP perf environment lately so I haven't gotten any numbers. When I do, I'll publish them on this thread.

Ethan's rationale is that it simplifies the code and we don't incur the memory overhead of allocating a hash map and this would outweigh the negative effect of possibly re-processing a packet from the same flow. Since userspace forwarding has gotten so much faster, this wouldn't be so bad.

Obviously, I need perf numbers to justify these claims; I will post them when I do.

Ryan Wilson
Member of Technical Staff
wryan at vmware.com
3401 Hillview Avenue, Palo Alto, CA
650.427.1511 Office
916.588.7783 Mobile

On May 9, 2014, at 8:25 AM, Ben Pfaff <blp at nicira.com> wrote:

> On Wed, May 07, 2014 at 03:14:01PM -0700, Ryan Wilson wrote:
>> The upcall hander keeps a hash table which hashes flow to a list of
>> corresponding packets. This used to be necessary as packets with the same flow
>> had similar actions and calculating actions used to be a performance bottleneck.
>> Now that userspace action calculation performance has improved, there is no need
>> for this hash map.
>> 
>> This patch removes this hash map and each packet has its own upcall.
>> 
>> Signed-off-by: Ryan Wilson <wryan at nicira.com>
> 
> Hmm.  Do we have performance numbers to back this up?  Ethan, I assume
> that you suggested this project; do you have additional rationale?

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