From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jiri Pirko <jiri@resnulli.us>
Cc: netdev@vger.kernel.org, davem@davemloft.net, jhs@mojatatu.com,
xiyou.wangcong@gmail.com, mlxsw@mellanox.com,
edumazet@google.com, daniel@iogearbox.net,
alexander.h.duyck@intel.com, willemb@google.com,
john.fastabend@gmail.com
Subject: Re: [patch net-next v3 2/2] net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath
Date: Wed, 1 Nov 2017 09:11:14 -0700 [thread overview]
Message-ID: <20171101161112.hpzl2a5oi5tdvauo@ast-mbp> (raw)
In-Reply-To: <20171101081803.GB1977@nanopsycho.orion>
On Wed, Nov 01, 2017 at 09:18:03AM +0100, Jiri Pirko wrote:
> Wed, Nov 01, 2017 at 03:12:50AM CET, alexei.starovoitov@gmail.com wrote:
> >On Tue, Oct 31, 2017 at 04:12:22PM +0100, Jiri Pirko wrote:
> >> From: Jiri Pirko <jiri@mellanox.com>
> >>
> >> In sch_handle_egress and sch_handle_ingress tp->q is used only in order
> >> to update stats. So stats and filter list are the only things that are
> >> needed in clsact qdisc fastpath processing. Introduce new mini_Qdisc
> >> struct to hold those items. Also, introduce a helper to swap the
> >> mini_Qdisc structures in case filter list head changes.
> >>
> >> This removes need for tp->q usage without added overhead.
> >>
> >> Signed-off-by: Jiri Pirko <jiri@mellanox.com>
> >> ---
> >> v2->v3:
> >> - Using head change callback to replace miniq pointer every time tp head
> >> changes. This eliminates one rcu dereference and makes the claim "without
> >> added overhead" valid.
> >
> >you kidding, right?
> >It's still two loads.
>
> I'm not.
> I replace:
>
> one rcu_dereference_bh(dev->egress_cl_list)
> by one rcu_dereference_bh(dev->miniq_egress)
>
> one dereference cl->q
> by one dereference miniq->filter_list
>
> What do I miss?
that in assembler code they are the same when debug is off ?
next prev parent reply other threads:[~2017-11-01 16:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 15:12 [patch net-next v3 0/2] net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath Jiri Pirko
2017-10-31 15:12 ` [patch net-next v3 1/2] net: sched: introduce chain_head_change callback Jiri Pirko
2017-10-31 15:12 ` [patch net-next v3 2/2] net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath Jiri Pirko
2017-11-01 2:12 ` Alexei Starovoitov
2017-11-01 8:18 ` Jiri Pirko
2017-11-01 16:11 ` Alexei Starovoitov [this message]
2017-11-02 11:27 ` Jiri Pirko
2017-11-01 10:25 ` Daniel Borkmann
2017-11-01 10:30 ` Jiri Pirko
2017-11-03 1:24 ` [patch net-next v3 0/2] " David Miller
2017-11-03 6:57 ` Jiri Pirko
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