netdev - Re: [Patch net 01/16] net_sched: introduce a workqueue for RCU callbacks of tc filter

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Date:   Fri, 27 Oct 2017 08:43:34 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Chris Mi <chrism@...lanox.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jiri Pirko <jiri@...nulli.us>,
        John Fastabend <john.fastabend@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [Patch net 01/16] net_sched: introduce a workqueue for RCU
 callbacks of tc filter

On Fri, Oct 27, 2017 at 4:55 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
>
> Would this be a good time for me to repeat my suggestion that timers
> be used to aggregate the work done in the workqueue handlers, thus
> decreasing the number of rcu_barrier() calls done under RTNL?
>

Yes, but not in this patchset. The current code is already so, therefore
needs a different patchset.

Quite contrarily, my patchset actually improves it _a little bit_ by moving
the second rcu_barrier() in current code base to a workqueue... The
contention is same, just that we no longer block tcf_block_put() path
with my patchset.