[ovs-dev] [PATCH 2/2] miniflow: Use 64-bit data.

[Jarno Rajahalme]

On Jan 6, 2015, at 1:20 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Tue, Jan 06, 2015 at 11:03:15AM -0800, Jarno Rajahalme wrote:
>> 
>> On Jan 5, 2015, at 2:39 PM, Ben Pfaff <blp at nicira.com> wrote:
>> 
>>> On Mon, Jan 05, 2015 at 02:15:13PM -0800, Ben Pfaff wrote:
>>>> On Mon, Jan 05, 2015 at 02:08:41PM -0800, Jarno Rajahalme wrote:
>>>>> 
>>>>> On Dec 29, 2014, at 2:27 PM, Ben Pfaff <blp at nicira.com> wrote:
>>>>> 
>>>>>> On Wed, Dec 17, 2014 at 10:30:42AM -0800, Jarno Rajahalme wrote:
>>>>>>> So far the compressed flow data in struct miniflow has been in 32-bit
>>>>>>> words with a 63-bit map, allowing for a maximum size of struct flow of
>>>>>>> 252 bytes.  With the forthcoming Geneve options this is not sufficient
>>>>>>> any more.
>>>>>>> 
>>>>>>> This patch solves the problem by changing the miniflow data to 64-bit
>>>>>>> words, doubling the flow max size to 504 bytes.  Since the word size
>>>>>>> is doubled, there is some loss in compression efficiency.  To counter
>>>>>>> this some of the flow fields have been reordered to keep related
>>>>>>> fields together (e.g., the source and destination IP addresses share
>>>>>>> the same 64-bit word).
>>>>>>> 
>>>>>>> This change should speed up flow data processing on 64-bit CPUs, which
>>>>>>> may help counterbalance the impact of making the struct flow bigger in
>>>>>>> the future.
>>>>>>> 
>>>>>>> Classifier lookup stage boundaries are also changed to 64-bit
>>>>>>> alignment, as the current algorithm depends on each miniflow word to
>>>>>>> not be split between ranges.  This has resulted in new padding (part
>>>>>>> of the 'mpls_lse' field).
>>>>>>> 
>>>>>>> The 'dp_hash' field is also moved to packet metadata to eliminate
>>>>>>> otherwise needed padding there.  This allows the L4 to fit into one
>>>>>>> 64-bit word, and also makes matches on 'dp_hash' more efficient as
>>>>>>> misses can be found already on stage 1.
>>>>>>> 
>>>>>>> Signed-off-by: Jarno Rajahalme <jrajahalme at nicira.com>
>>>>> 
>>>>>> This seems mostly straightforward.  Are there particular parts you'd
>>>>>> like me to look over carefully?
>>>>>> 
>>>>> 
>>>>> Maybe the changes to the miniflow push macros, which get a bit more
>>>>> complicated...
>>>> 
>>>> OK, I'll do that in a bit.
>>> 
>>> I read them through them.  I didn't spot any bugs, although they're
>>> somewhat tricky.
>> 
>> Is this an Acked-by then?
> 
> Acked-by: Ben Pfaff <blp at nicira.com>

Thanks for the review, pushed to master.

  Jarno