Re: IFQ_ENQUEUE argument refactor (was Re: RFC: ALTQ caller refactor)

[Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>]

Hi,

On 2016/03/07 22:20, Kengo NAKAHARA wrote:
> Hi,
> 
> On 2016/03/07 19:20, Joerg Sonnenberger wrote:
>> On Tue, Feb 23, 2016 at 01:52:40PM +0900, Kengo NAKAHARA wrote:
>>> Hi,
>>>
>>> I want to uniform IFQ_ENQUEUE arguments whether ALTQ is defined or not.
>>> # And I also want to eliminate ALTQ_DECL and ALTQ_COMMA macros...
>>>  So, I make struct altq_pktattr from IFQ_CLASSIFY and IFQ_ENQUEUE argument
>>> to m_tag. Here is the patch.
>>>     http://netbsd.org/~knakahara/altq-caller-refactor/altq-caller-refactor.patch
>>>
>>> In above patch, I fix performance issue by the following two ways.
>>>     - make ALTQ's m_tag pool cache
>>>     - inline altq_*_pattr functions
>>> Without these two fixes, the enabled ALTQ throughput degraded about 10%.
>>> However, with these two fixes, the throughput is almost the same
>>> performance.
>>
>> Is there a good reason to keep the complexity of the pattr attribute
>> around? From working on the ALTQ code a few years ago I remember that it
>> is only used by some of the more experimental mechanisms and not used by
>> the few queueing disciplines people normally care about. It might be
>> easier to just get rid of it.
> 
> No, there is no good reason. But, that is out of my scope now.
> Sorry about confusing mail title, I want to remove pattr argument from
> IFQ_ENQUEUE to support TX multiqueue. The lack of TX multiqueue causes
> critical scaling problem because of lock contention in IFQ_ENQUEUE and
> ifp->if_start. To avoid this lock contention, that is, support TX
> multiqueue, I think it is require to support ifp->if_transmit() which
> pass mbuf to ifp directly without IFQ_ENQUEUE. To implement this
> interface with backward compatibility(keep IFQ_ENQUEUE + ifp->if_start
> interface for many network device drivers), it is required to remove
> pattr from IFQ_ENQUEUE.
> 
> BTW, I am not sure that it is the best solution to put struct altq_pktattr
> to mbuf to simplify ALTQ... As you may know, the comment in ip_input()
> says "ALTQ is changed to use a pfil hook".
>     http://nxr.netbsd.org/xref/src/sys/netinet/ip_input.c#554 
> FreeBSD and OpenBSD modified ALTQ by such way. However, I am not sure
> that whether the way fits to NetBSD...

I rebase and modify a little(use container_of). Here is the patch.
    http://www.netbsd.org/~knakahara/ifq-enqueue-refactor/ifq-enqueue-refactor.patch

Does anyone have Any comments? Any comments are welcome.


Thanks,

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Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>