linux-kernel - Re: [RFC V2 PATCH 17/25] net/netpolicy: introduce netpolicy_pick

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Date:	Fri, 05 Aug 2016 00:39:00 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	John Fastabend <john.fastabend@...il.com>, kan.liang@...el.com,
	davem@...emloft.net, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
CC:	mingo@...hat.com, peterz@...radead.org, kuznet@....inr.ac.ru,
	jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
	akpm@...ux-foundation.org, keescook@...omium.org,
	viro@...iv.linux.org.uk, gorcunov@...nvz.org,
	john.stultz@...aro.org, aduyck@...antis.com, ben@...adent.org.uk,
	decot@...glers.com, fw@...len.de, alexander.duyck@...il.com,
	tom@...bertland.com, rdunlap@...radead.org,
	xiyou.wangcong@...il.com, hannes@...essinduktion.org,
	jesse.brandeburg@...el.com, andi@...stfloor.org
Subject: Re: [RFC V2 PATCH 17/25] net/netpolicy: introduce netpolicy_pick_queue

On 08/04/2016 10:21 PM, John Fastabend wrote:
> On 16-08-04 12:36 PM, kan.liang@...el.com wrote:
>> From: Kan Liang <kan.liang@...el.com>
>>
>> To achieve better network performance, the key step is to distribute the
>> packets to dedicated queues according to policy and system run time
>> status.
>>
>> This patch provides an interface which can return the proper dedicated
>> queue for socket/task. Then the packets of the socket/task will be
>> redirect to the dedicated queue for better network performance.
>>
>> For selecting the proper queue, currently it uses round-robin algorithm
>> to find the available object from the given policy object list. The
>> algorithm is good enough for now. But it could be improved by some
>> adaptive algorithm later.
>>
>> The selected object will be stored in hashtable. So it does not need to
>> go through the whole object list every time.
>>
>> Signed-off-by: Kan Liang <kan.liang@...el.com>
>> ---
>>   include/linux/netpolicy.h |   5 ++
>>   net/core/netpolicy.c      | 136 ++++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 141 insertions(+)
>
> There is a hook in the tx path now (recently added)
>
> # ifdef CONFIG_NET_EGRESS
>          if (static_key_false(&egress_needed)) {
>                  skb = sch_handle_egress(skb, &rc, dev);
>                  if (!skb)
>                          goto out;
>          }
> # endif
>
> that allows pushing any policy you like for picking tx queues. It would
> be better to use this mechanism. The hook runs 'tc' classifiers so
> either write a new ./net/sch/cls_*.c for this or just use ebpf to stick
> your policy in at runtime.
>
> I'm out of the office for a few days but when I get pack I can test that
> it actually picks the selected queue in all cases I know there was an
> issue with some of the drivers using select_queue awhile back.

+1, I tried to bring this up here [1] in the last spin. I think only very
few changes would be needed, f.e. on eBPF side to add a queue setting
helper function which is probably straight forward ~10loc patch; and with
regards to actually picking it up after clsact egress, we'd need to adapt
__netdev_pick_tx() slightly when CONFIG_XPS so it doesn't override it.

   [1] http://www.spinics.net/lists/netdev/msg386953.html