linux-kernel - Re: [PATCH V2] X86/CPU: Avoid 100ms sleep for cpu offline during S3

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Date:	Tue, 12 Aug 2014 09:55:41 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Lan Tianyu <tianyu.lan@...el.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, toshi.kani@...com, imammedo@...hat.com,
	mingo@...nel.org, prarit@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] X86/CPU: Avoid 100ms sleep for cpu offline  during S3

On Tue, Aug 12, 2014 at 03:31:06PM +0800, Lan Tianyu wrote:
> With some bad kernel configures, cpu offline consumes more than 100ms
> during S3. This because native_cpu_die() would fall into 100ms
> sleep when cpu idle loop thread marked cpu state to DEAD slower. It's
> timing related issue. What native_cpu_die() does is that poll cpu
> state and wait for 100ms if cpu state hasn't been marked to DEAD.
> The 100ms sleep doesn't make sense. To avoid such long sleep, this
> patch is to add struct completion to each cpu, wait for the completion
> in the native_cpu_die() and wakeup the completion when the cpu state is
> marked to DEAD.
> 
> Tested on the Intel Xeon server with 48 cores, Ivbridge and Haswell laptops.

... and on an AMD laptop.

> the times of cpu offline on these machines are reduced from more than 100ms
> to less than 5ms. The system suspend time reduces 2.3s on the servers.
> 
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>

Acked-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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