linux-kernel - Re: [PATCH tip/core/rcu] Reduce overhead of cond

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Date:	Mon, 23 Jun 2014 17:20:30 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	ak@...ux.intel.com, cl@...two.org, umgwanakikbuti@...il.com
Subject: Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks
 for RCU

On 06/23/2014 05:15 PM, Paul E. McKenney wrote:
> Just out of curiosity, how many CPUs does your system have?  80?
> If 160, looks like something bad is happening at 80.

80 cores, 160 threads.  >80 processes/threads is where we start using
the second thread on the cores.  The tasks are also pinned to
hyperthread pairs, so they disturb each other, and the scheduler moves
them between threads on occasion which causes extra noise.
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