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From: Nick Piggin <piggin@cyberone.com.au>
To: dipankar@in.ibm.com
Cc: linux-kernel@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>,
	Paul McKenney <paul.mckenney@us.ibm.com>
Subject: Re: [patch] RCU for low latency [1/2]
Date: Fri, 09 Jan 2004 02:12:00 +1100	[thread overview]
Message-ID: <3FFD7340.7050209@cyberone.com.au> (raw)
In-Reply-To: <20040108114958.GB5128@in.ibm.com>



Dipankar Sarma wrote:

>Provide a rq_has_rt_task() interface to detect runqueues with
>real time priority tasks. Useful for RCU optimizations.
>

Can you make rq_has_rt_task the slow path? Adding things like this
can actually be noticable on microbenchmarks (eg. pipe based ctx
switching). Its probably cache artifacts that I see, but it wouldn't
hurt to keep the scheduler as tight as possible.

I think this should cover it.

int rq_has_rt_task(int cpu)
{
	runqueue_t *rq = cpu_rq(cpu);
	return (sched_find_first_bit(rq->active) < MAX_RT_PRIO);
}

Any good?




  parent reply	other threads:[~2004-01-08 15:13 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-01-08 11:48 [patch] RCU for low latency [0/1] Dipankar Sarma
2004-01-08 11:49 ` [patch] RCU for low latency [1/2] Dipankar Sarma
2004-01-08 11:50   ` [patch] RCU for low latency [2/2] Dipankar Sarma
2004-01-08 23:43     ` Rusty Russell
2004-01-14  8:24       ` Dipankar Sarma
2004-01-14 23:35         ` Rusty Russell
2004-01-15  6:03           ` Dipankar Sarma
2004-01-19 23:25             ` Rusty Russell
2004-01-20  1:22               ` Lincoln Dale
2004-01-08 15:12   ` Nick Piggin [this message]
2004-01-08 19:33     ` [patch] RCU for low latency [1/2] Dipankar Sarma

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