netdev - Re: [net-next v3 2/2] net: sched: support hash/classid/cpuid selecting tx queue

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Date:   Mon, 13 Dec 2021 14:53:25 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexander Lobakin <alobakin@...me>,
        Paolo Abeni <pabeni@...hat.com>,
        Talal Ahmad <talalahmad@...gle.com>,
        Kevin Hao <haokexin@...il.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Antoine Tenart <atenart@...nel.org>,
        Wei Wang <weiwan@...gle.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [net-next v3 2/2] net: sched: support hash/classid/cpuid
 selecting tx queue

On Sat, Dec 11, 2021 at 6:34 PM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
>
> On Sun, Dec 12, 2021 at 10:19 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
> > On Thu, Dec 9, 2021 at 6:36 PM <xiangxia.m.yue@...il.com> wrote:
> > >
> > > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > >
> > > This patch allows users to select queue_mapping, range
> > > from A to B. And users can use skb-hash, cgroup classid
> > > and cpuid to select Tx queues. Then we can load balance
> > > packets from A to B queue. The range is an unsigned 16bit
> > > value in decimal format.
> > >
> > > $ tc filter ... action skbedit queue_mapping hash-type normal A B
> > >
> > > "skbedit queue_mapping QUEUE_MAPPING" (from "man 8 tc-skbedit") is
> > > enhanced with flags:
> > > * SKBEDIT_F_QUEUE_MAPPING_HASH
> > > * SKBEDIT_F_QUEUE_MAPPING_CLASSID
> > > * SKBEDIT_F_QUEUE_MAPPING_CPUID
> >
> > With act_bpf you can do all of them... So why do you have to do it
> > in skbedit?
> Hi Cong
> This idea is inspired by skbedit queue_mapping, and skbedit is
> enhanced by this patch.

This is exactly my question. ;)

> We support this in skbedit firstly in production. act_bpf can do more
> things than this. Anyway we
> can support this in both act_skbedit/acc_bpf. 1/2 is changed from
> skip_tx_queue in skb to per-cpu var suggested-by Eric. We need another
> patch which can change the
> per-cpu var in bpf. I will post this patch later.

The point is if act_bpf can do it, you don't need to bother skbedit at
all. More importantly, you are enforcing policies in kernel, which is
not encouraged. So unless you provide more details, this patch is not
needed at all.

Thanks.