From: Andi Kleen <andi@firstfloor.org>
To: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Track accurate idle time with tick_sched.idle_sleeptime
Date: 02 Sep 2007 00:23:53 +0200 [thread overview]
Message-ID: <p73bqcmvxc6.fsf@bingen.suse.de> (raw)
In-Reply-To: <20070827215611.GA30396@linux-os.sc.intel.com>
Venki Pallipadi <venkatesh.pallipadi@intel.com> writes:
>
> +void tick_nohz_stop_idle(int cpu)
> +{
> + struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
> +
> + if (ts->idle_active) {
> + ktime_t now, delta;
> + now = ktime_get();
That could be PM timer read costing thousands of cycles.
For going into idle it's probably not a real problem, but it could
seriously affect out of idle latencies.
You would really need a cheaper per CPU timer that doesn't
stop in idle (which rules out sched_clock). It's all unfortunately
quite messy.
-Andi
next prev parent reply other threads:[~2007-09-01 22:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-27 21:56 [PATCH] Track accurate idle time with tick_sched.idle_sleeptime Venki Pallipadi
2007-08-31 18:22 ` Ingo Molnar
2007-08-31 18:24 ` Ingo Molnar
2007-08-31 18:26 ` Pallipadi, Venkatesh
2007-09-01 22:23 ` Andi Kleen [this message]
2007-09-02 7:28 ` Ingo Molnar
2007-09-02 7:46 ` Andi Kleen
2007-09-02 10:02 ` Ingo Molnar
2007-09-10 18:59 ` Pallipadi, Venkatesh
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