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From: Chris Friesen <chris.friesen@windriver.com>
To: Sean V Kelley <sean.v.kelley@intel.com>,
	Bjorn Helgaas <helgaas@kernel.org>
Cc: linux-pci@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nitesh Narayan Lal <nitesh@redhat.com>
Subject: Re: PCI, isolcpus, and irq affinity
Date: Mon, 12 Oct 2020 13:18:22 -0600	[thread overview]
Message-ID: <99c9fb9a-d281-28f8-59a3-aa1f23a12261@windriver.com> (raw)
In-Reply-To: <3FF15DD8-72AF-4C1D-BF66-248FC87FD903@intel.com>

On 10/12/2020 11:39 AM, Sean V Kelley wrote:

> Are you attempting a tick-less run?  I’ve seen the NO_HZ_FULL (full 
> dynticks) feature behave somewhat inconsistently when PREEMPT_RT is 
> enabled.  The timer ticks suppression feature can at times appear to be 
> not functioning. I’m curious about how you are attempting to isolate the 
> cores.

We're trying to run tickess on a subset of the CPUs, using a combination 
of isolcpus, irqaffinity, rcu_nocbs, and nohz_full boot args, as well as 
runtime affinity adjustment for tasks and IRQs.

I don't think we're seeing full suppression of timer ticks, but partial 
suppression is happening.  Application CPUs are showing as low as 10K 
interrupts for LOC while the housekeeping CPUs are 300-500 million.

Chris

  reply	other threads:[~2020-10-12 19:18 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 15:49 Chris Friesen
2020-10-12 16:58 ` Bjorn Helgaas
2020-10-12 17:39   ` Sean V Kelley
2020-10-12 19:18     ` Chris Friesen [this message]
2020-10-12 17:42   ` Nitesh Narayan Lal
2020-10-12 17:50   ` Thomas Gleixner
2020-10-12 18:58     ` Chris Friesen
2020-10-12 19:07       ` Keith Busch
2020-10-12 19:44         ` Thomas Gleixner
2020-10-15 18:47         ` Chris Friesen
2020-10-15 19:02           ` Keith Busch
2020-10-12 19:31       ` Thomas Gleixner
2020-10-12 20:24         ` David Woodhouse
2020-10-12 22:25           ` Thomas Gleixner

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