From: Jakub Kicinski <kuba@kernel.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>, Yan Zhai <yan@cloudflare.com>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>, Jiri Pirko <jiri@resnulli.us>,
Simon Horman <horms@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Coco Li <lixiaoyan@google.com>, Wei Wang <weiwan@google.com>,
Alexander Duyck <alexanderduyck@fb.com>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
bpf@vger.kernel.org, kernel-team@cloudflare.com
Subject: Re: [PATCH] net: raise RCU qs after each threaded NAPI poll
Date: Wed, 28 Feb 2024 07:35:44 -0800 [thread overview]
Message-ID: <20240228073544.791ae897@kernel.org> (raw)
In-Reply-To: <9a0052f9-b022-42c9-a5da-1d6ca3b00885@paulmck-laptop>
On Wed, 28 Feb 2024 07:15:42 -0800 Paul E. McKenney wrote:
> > > Another complication is that although CONFIG_PREEMPT_RT kernels are
> > > built with CONFIG_PREEMPT_RCU, the reverse is not always the case.
> > > And if we are not repolling, don't we have a high probability of doing
> > > a voluntary context when we reach napi_thread_wait() at the beginning
> > > of that loop?
> >
> > Very much so, which is why adding the cost of rcu_softirq_qs()
> > for every NAPI run feels like an overkill.
>
> Would it be better to do the rcu_softirq_qs() only once every 1000 times
> or some such? Or once every HZ jiffies?
>
> Or is there a better way?
Right, we can do that. Yan Zhai, have you measured the performance
impact / time spent in the call?
next prev parent reply other threads:[~2024-02-28 15:35 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 15:44 [PATCH] net: raise RCU qs after each threaded NAPI poll Yan Zhai
2024-02-27 16:44 ` Eric Dumazet
2024-02-27 18:32 ` Paul E. McKenney
2024-02-27 21:22 ` Yan Zhai
2024-02-27 22:58 ` Paul E. McKenney
2024-02-28 3:10 ` Jakub Kicinski
2024-02-28 4:42 ` Paul E. McKenney
2024-02-28 14:43 ` Jakub Kicinski
2024-02-28 15:15 ` Paul E. McKenney
2024-02-28 15:35 ` Jakub Kicinski [this message]
2024-02-28 15:57 ` Yan Zhai
2024-02-28 11:50 ` Toke Høiland-Jørgensen
2024-02-28 15:10 ` Paul E. McKenney
2024-02-28 15:48 ` Yan Zhai
2024-02-28 17:47 ` Paul E. McKenney
2024-02-28 15:37 ` Joel Fernandes
2024-02-28 16:37 ` Yan Zhai
2024-02-28 17:18 ` Paul E. McKenney
2024-02-28 20:14 ` Joel Fernandes
2024-02-28 21:13 ` Paul E. McKenney
2024-02-28 21:27 ` Joel Fernandes
2024-02-28 21:52 ` Paul E. McKenney
2024-02-28 22:10 ` Joel Fernandes
2024-02-28 22:19 ` Paul E. McKenney
2024-02-28 22:33 ` Steven Rostedt
2024-02-28 22:48 ` Alexei Starovoitov
2024-02-28 22:58 ` Paul E. McKenney
2024-02-29 14:21 ` Joel Fernandes
2024-02-29 16:57 ` Paul E. McKenney
2024-02-29 17:41 ` Joel Fernandes
2024-02-29 18:29 ` Paul E. McKenney
2024-03-02 2:24 ` Joel Fernandes
2024-03-03 0:25 ` Paul E. McKenney
2024-03-03 1:01 ` Joel Fernandes
2024-03-04 9:16 ` Joel Fernandes
2024-03-05 17:53 ` Paul E. McKenney
2024-03-05 19:57 ` Mark Rutland
2024-03-05 21:52 ` Paul E. McKenney
2024-03-06 16:56 ` Steven Rostedt
2024-03-07 16:57 ` Mark Rutland
2024-03-07 18:34 ` Mark Rutland
2024-03-07 18:52 ` Steven Rostedt
2024-03-07 18:58 ` Paul E. McKenney
2024-03-04 9:16 ` Joel Fernandes
2024-02-28 22:49 ` Paul E. McKenney
2024-02-27 21:17 ` Yan Zhai
2024-02-28 23:53 ` Yan Zhai
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