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From: Frederic Weisbecker <frederic@kernel.org>
To: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Cc: paulmck@kernel.org, joel@joelfernandes.org,
	josh@joshtriplett.org, boqun.feng@gmail.com, rostedt@goodmis.org,
	mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
	qiang.zhang1211@gmail.com, rcu@vger.kernel.org,
	linux-kernel@vger.kernel.org, neeraj.upadhyay@kernel.org
Subject: Re: [PATCH] rcu: Reduce synchronize_rcu() delays when all wait heads are in use
Date: Wed, 13 Mar 2024 18:05:00 +0100	[thread overview]
Message-ID: <ZfHcvI54IrbQTjbP@localhost.localdomain> (raw)
In-Reply-To: <35e009c4-d52c-4b96-ba10-afa0be9dfd5e@amd.com>

Le Wed, Mar 13, 2024 at 09:41:58PM +0530, Neeraj Upadhyay a écrit :
> > Also there is a risk that this non-wait-head gets later assigned as
> > rcu_state.srs_done_tail. And then this pending sr may not be completed
> > until the next grace period calling rcu_sr_normal_gp_cleanup()? (Because
> > the work doesn't take care of rcu_state.srs_done_tail itself). And then
> > the delay can be arbitrary.
> > 
> 
> That is correct. Only the first node suffers from deferred GP.
> If there are large number of callbacks which got added after
> last available wait head was queued, all those callbacks (except one)
> can still have a GP assigned to them.

Oh and yes I missed the fact that you still reissue a GP while queueing
a non wait-head as ->srs_wait_tail. That point looks good.

Thanks.

      parent reply	other threads:[~2024-03-13 17:05 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-13  8:32 [PATCH] rcu: Reduce synchronize_rcu() delays when all wait heads are in use Neeraj Upadhyay
2024-03-13 14:40 ` Joel Fernandes
2024-03-13 16:04   ` Neeraj Upadhyay
2024-03-13 16:13     ` Joel Fernandes
2024-03-13 16:19       ` Neeraj Upadhyay
2024-03-13 15:18 ` Frederic Weisbecker
2024-03-13 16:11   ` Neeraj Upadhyay
2024-03-13 16:43     ` Frederic Weisbecker
2024-03-13 16:54       ` Neeraj Upadhyay
2024-03-13 17:15         ` Frederic Weisbecker
2024-03-13 17:26           ` Neeraj Upadhyay
2024-03-13 17:49             ` Neeraj Upadhyay
2024-03-13 23:22               ` Frederic Weisbecker
2024-03-13 17:05     ` Frederic Weisbecker [this message]

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