[ovs-dev] [PATCH] bond: raise minimal bond distribution per interface

[YAMAMOTO Takashi]

> On Wed, May 7, 2014 at 7:01 PM, YAMAMOTO Takashi <yamamoto at valinux.co.jp> wrote:
>>> Sorry I was not clear in the commit message. It is the average of the
>>> first interface. I will make it clear before pushing.
>>
>> thanks for clarification.
>> i think the average is not so important.  hash colision is.
>> the worst case is, two interfaces in the same bucket, one in the other.
>> in that case, packet distribution would be 1:1:2.
> Would you please explain more? How did you arrive at this
> distribution? Why is this the worst case?

see hmap_random_node.

given the number of items is 3, there are a few possible cases:
- a bucket has all 3 items.
- a bucket has 2 items, and another bucket has 1 item.
- 3 buckets, each has 1 item.

for the first and last cases distribution would be 1:1:1.

for the 2nd case, each bucket would have the same chance to be selected.

YAMAMOTO Takashi

>> your value is safe enough for the distribution.
>>
>> YAMAMOTO Takashi
>>
>>>
>>> On Wed, May 7, 2014 at 6:18 PM, YAMAMOTO Takashi <yamamoto at valinux.co.jp> wrote:
>>>>> Raise the minimal per interface packet distribution from 7 to 24.
>>>>>
>>>>> With 256 packet distributing to 3 interfaces, the expected packets per
>>>>> interface should be 256/3 = 85.3
>>>>>
>>>>> Tested with 200 runs, the average number of packet per interface is
>>>>> 85.9. close to the expected number, standard deviation within the 200
>>>>> run is 24.4. Tested with 2x standard deviation with 10K test runs,
>>>>> got around 0.1% failure rate. 2.5x standard deviation passes 100K test
>>>>> runs without failure.
>>>>>
>>>>> Using 2.5x for the unit test, 83.5 - 2.5 * 24.4, Round down to the
>>>>> whole number of 24.
>>>>
>>>> the patch itself looks ok (thus acked-by) but i have a question on
>>>> the commit message.
>>>> why can the average number be larger than the expected number?
>>>> the total number of packets for a run is expected to be exactly 256,
>>>> isn't it?
>>>>
>>>> Acked-by: YAMAMOTO Takashi <yamamoto at valinux.co.jp>
>>>> Tested-by: YAMAMOTO Takashi <yamamoto at valinux.co.jp>
>>>>
>>>> YAMAMOTO Takashi
>>>>
>>>>>
>>>>> Signed-off-by: Andy Zhou <azhou at nicira.com>
>>>>> ---
>>>>>  tests/ofproto-dpif.at | 6 +++---
>>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at
>>>>> index c46e997..3723459 100644
>>>>> --- a/tests/ofproto-dpif.at
>>>>> +++ b/tests/ofproto-dpif.at
>>>>> @@ -191,9 +191,9 @@ AT_CHECK([ovs-appctl dpif/dump-flows br0 |grep tcp > br0_flows.txt])
>>>>>  AT_CHECK([ovs-appctl dpif/dump-flows br1 |grep tcp > br1_flows.txt])
>>>>>  # Make sure there is resonable distribution to all three ports.
>>>>>  # We don't want to make this check precise, in case hash function changes.
>>>>> -AT_CHECK([test `grep in_port.4 br1_flows.txt |wc -l` -gt 7])
>>>>> -AT_CHECK([test `grep in_port.5 br1_flows.txt |wc -l` -gt 7])
>>>>> -AT_CHECK([test `grep in_port.6 br1_flows.txt |wc -l` -gt 7])
>>>>> +AT_CHECK([test `grep in_port.4 br1_flows.txt |wc -l` -gt 24])
>>>>> +AT_CHECK([test `grep in_port.5 br1_flows.txt |wc -l` -gt 24])
>>>>> +AT_CHECK([test `grep in_port.6 br1_flows.txt |wc -l` -gt 24])
>>>>>  OVS_VSWITCHD_STOP()
>>>>>  AT_CLEANUP
>>>>>
>>>>> --
>>>>> 1.9.1
>>>>>
>>>>> _______________________________________________
>>>>> dev mailing list
>>>>> dev at openvswitch.org
>>>>> http://openvswitch.org/mailman/listinfo/dev
>>> _______________________________________________
>>> dev mailing list
>>> dev at openvswitch.org
>>> http://openvswitch.org/mailman/listinfo/dev
> _______________________________________________
> dev mailing list
> dev at openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev