linux-kernel - Re: [PATCH 1/2] x86/intel_rdt/mbm: Fix MBM overflow handler during hot cpu

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Message-ID: <alpine.DEB.2.20.1708161117450.1987@nanos>
Date:   Wed, 16 Aug 2017 11:19:45 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>
cc:     vikas.shivappa@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, hpa@...or.com, peterz@...radead.org,
        ravi.v.shankar@...el.com, tony.luck@...el.com,
        fenghua.yu@...el.com, ak@...ux.intel.com, eranian@...gle.com,
        davidcc@...gle.com
Subject: Re: [PATCH 1/2] x86/intel_rdt/mbm: Fix MBM overflow handler during
 hot cpu

On Tue, 15 Aug 2017, Vikas Shivappa wrote:
> When a CPU is dying, we cancel the worker and schedule a new worker on a
> different CPU on the same domain. But if the timer is already about to
> expire (say 0.99s) then we essentially double the interval.
> 
> We modify the hot cpu handling to cancel the delayed work on the dying
> cpu and run the worker immediately on a different cpu in same domain. We
> donot flush the worker because the MBM overflow worker reschedules the
> worker on same CPU and scans the domain->cpu_mask to get the domain
> pointer.

You could alternatively use flush and make the worker code schedule the
work on a still online CPU in the domain instead of blindly rescheduling it
on the same CPU.

Thanks,

	tglx