netdev - Re: [net-next v5 2/2] net: sched: support hash/classid/cpuid selecting tx queue

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Message-ID: <CAMDZJNXuj7CL=0n=nL31zuZ5+_fzOQjX8Ftk2n6TQVgd75UnLA@mail.gmail.com>
Date:   Wed, 29 Dec 2021 20:50:54 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Cong Wang <xiyou.wangcong@...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 v5 2/2] net: sched: support hash/classid/cpuid
 selecting tx queue

On Sat, Dec 25, 2021 at 9:41 AM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
>
> On Sat, Dec 25, 2021 at 3:26 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
> >
> > On Tue, Dec 21, 2021 at 5:24 PM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
> > >
> > > On Tue, Dec 21, 2021 at 1:57 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
> > > >
> > > > On Mon, Dec 20, 2021 at 4:39 AM <xiangxia.m.yue@...il.com> wrote:
> > > > >
> > > > > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > > > >
> > > > > This patch allows user to select queue_mapping, range
> > > > > from A to B. And user can use skbhash, 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 skbhash A B
> > > > >
> > > > > "skbedit queue_mapping QUEUE_MAPPING" (from "man 8 tc-skbedit")
> > > > > is enhanced with flags:
> > > > > * SKBEDIT_F_TXQ_SKBHASH
> > > > > * SKBEDIT_F_TXQ_CLASSID
> > > > > * SKBEDIT_F_TXQ_CPUID
> > > >
> > > > Once again, you are enforcing policies in kernel, which is not good.
> > > > Kernel should just set whatever you give to it, not selecting policies
> > > > like a menu.
> > > I agree that, but for tc/net-sched layer, there are a lot of
> >
> > If you agree, why still move on with this patch? Apparently
> > you don't. ;)
> >
> > > networking policies, for example , cls_A, act_B, sch_C.
> >
> > You are justifying your logic by shifting the topics here.
> Hi Cong,
> I mean that if the "policies" are networking policies, I don't agree
> with you, because
> the TC(or net sched layer), are networking policies, right ? and this
> patch enhances the original feature of TC.
>
>
> > The qdisc algorithm is very different from your case, it is essentially
> > hard, if not impossible, to completely move to user-space. Even if we
> > had eBPF based Qdisc, its programmablility is still very limited.
> > Your code is much much much easier, which is essentially one-line,
> > hence you have to reason to compare it with this, nor you can even
> > justify it.
> I think we have talked about this in another thread. And other
> maintainers comment on this.
> > > > Any reason why you can't obtain these values in user-space?
> > > Did you mean that we add this flags to iproute2 tools? This patch for
> > > iproute2, is not post. If the kerenl patches are accepted, I will send
> > > them.
> >
> > Nope, I mean you can for example, obtain the CPU ID in user-space
> > and pass it directly to _current_ act_skbedit as it is.
> This flag is passed from userspace. Do you mean the cpuid value should
> be passed from userspace?
> If so, this is not what we need. because we don't know which one cpu
> the pod(containers) will use. and for skb-hash/classid
> this helps us to pick the tx queue from a range. I don't understand
> why this value should be passed from userspace. How ?
> can you give me examples ?
friendly ping
> BTW, this patch is the core of patchset.
> > Thanks.
>
>
>
> --
> Best regards, Tonghao



-- 
Best regards, Tonghao