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From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>
Subject: [RFC 0/5] rcu: Introduce leaf_node_for_each_mask_possible_cpu() and its friend
Date: Fri,  9 Dec 2016 16:48:22 +0800	[thread overview]
Message-ID: <20161209084828.11827-1-boqun.feng@gmail.com> (raw)

Hi Paul,

While reading the discussion at:

https://marc.info/?l=linux-kernel&m=148044253400769

I figured we might use this fact to save some extra checks in RCU core code,
currently we iterate over all the possible CPUs on a leaf node, check whether
they were masked in a certain mask and do something. However, given the fact
that the masks on a leaf node should always be sparse than the corresponding
part of cpu_possible_mask, we'd better iterate over all bits in a mask and
check whether the corresponding CPU is possible or not.

So I made this RFC, I did a simple build/boot/rcutorture test on my box with
SMP=4, nothing bad happens. Currently I'm waiting for the 0day and trying to
test this one a bigger system, in the meanwhile, looking forwards to any
comment and suggestion.

So thoughts?

Regards,
Boqun

             reply	other threads:[~2016-12-09  8:49 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-09  8:48 Boqun Feng [this message]
2016-12-09  8:48 ` [RFC 1/5] rcu: Introduce primitives to iterate mask bits in an RCU leaf node Boqun Feng
2016-12-09  8:48 ` [RFC 2/5] rcu: Use leaf_node_for_each_mask_possible_cpu() in RCU stall checking Boqun Feng
2016-12-09  8:48 ` [RFC 3/5] rcu: Use leaf_node_for_each_mask_possible_cpu() for ->expmask iteration Boqun Feng
2016-12-09  8:48 ` [RFC 4/5] rcu: Use leaf_node_for_each_mask_possible_cpu() in force_qs_rnp() Boqun Feng
2016-12-09  8:48 ` [RFC 5/5] rcu: Use leaf_node_for_each_mask_*() for leaf node online CPU iteration Boqun Feng
2016-12-09 23:49 ` [RFC 0/5] rcu: Introduce leaf_node_for_each_mask_possible_cpu() and its friend Paul E. McKenney
2016-12-10  0:45   ` Boqun Feng
2016-12-10  4:28     ` Paul E. McKenney
2016-12-10 13:36       ` Boqun Feng
2016-12-10 17:38         ` Paul E. McKenney
2016-12-11  0:06           ` Boqun Feng

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