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From: Eliezer Tamir <eliezer.tamir@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	lenb@kernel.org, rjw@rjwysocki.net,
	David Miller <davem@davemloft.net>,
	rui.zhang@intel.com, jacob.jun.pan@linux.intel.com,
	Mike Galbraith <bitbucket@online.de>,
	Ingo Molnar <mingo@kernel.org>,
	hpa@zytor.com, Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 7/8] sched, net: Fixup busy_loop_us_clock()
Date: Thu, 28 Nov 2013 18:49:00 +0200	[thread overview]
Message-ID: <529773FC.6020707@linux.intel.com> (raw)
In-Reply-To: <20131126160815.293633156@infradead.org>

On 26/11/2013 17:57, Peter Zijlstra wrote:
> 
> Replace sched_clock() usage with local_clock() which has a bounded
> drift between CPUs (<2 jiffies).
> 

Peter,

I have tested this patch and I see a performance regression of about
1.5%.

Maybe it would be better, rather then testing in the fast path, to
simply disallow busy polling altogether when sched_clock_stable is
not true?

Thanks,
Eliezer

  reply	other threads:[~2013-11-28 16:49 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-26 15:57 [PATCH 0/8] Cure faux idle wreckage Peter Zijlstra
2013-11-26 15:57 ` [PATCH 1/8] x86, acpi, idle: Restructure the mwait idle routines Peter Zijlstra
2013-11-26 15:57 ` [PATCH 2/8] sched, preempt: Fixup missed PREEMPT_NEED_RESCHED folding Peter Zijlstra
2013-11-26 15:57 ` [PATCH 3/8] idle, thermal, acpi: Remove home grown idle implementations Peter Zijlstra
2013-11-26 15:57 ` [PATCH 4/8] preempt, locking: Rework local_bh_{dis,en}able() Peter Zijlstra
2013-11-26 15:57 ` [PATCH 5/8] locking: Optimize lock_bh functions Peter Zijlstra
2013-11-26 15:57 ` [PATCH 6/8] sched, net: Clean up preempt_enable_no_resched() abuse Peter Zijlstra
2013-11-26 15:57 ` [PATCH 7/8] sched, net: Fixup busy_loop_us_clock() Peter Zijlstra
2013-11-28 16:49   ` Eliezer Tamir [this message]
2013-11-28 17:40     ` Peter Zijlstra
2013-11-28 18:50       ` Peter Zijlstra
2013-11-29 13:52       ` Eliezer Tamir
2013-11-26 15:57 ` [PATCH 8/8] preempt: Take away preempt_enable_no_resched() from modules Peter Zijlstra
2013-11-26 23:23 ` [PATCH 0/8] Cure faux idle wreckage Jacob Pan

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