linux-kernel - Re: 4.2: CONFIG_NO_HZ_FULL_ALL effectively disabling non-boot CPUs

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Message-ID: <alpine.LRH.2.20.1510111026340.28155@math.ut.ee>
Date:	Sun, 11 Oct 2015 10:27:54 +0300 (EEST)
From:	Meelis Roos <mroos@...ux.ee>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: 4.2: CONFIG_NO_HZ_FULL_ALL effectively disabling non-boot CPUs

> > Short summary: turning on CONFIG_NO_HZ_FULL_ALL seems to disable all 
> > non-boot CPUs for scheduler.

[...]

> This is expected and intended behavior.  The whole point of
> CONFIG_NO_HZ_FULL_ALL is to keep everything off of the non-boot CPUs
> that is not explicitly placed there.  Without CONFIG_NO_HZ_FULL_ALL,
> you can use the nohz_full boot parameter to select exactly which
> CPUs are to behave this way.

OK, thanks - disabled it on my desktops anyway now.

Perhaps the Kconfig description of it should explian the consequences 
more clearly so other people do not stumble upon it like I did?

-- 
Meelis Roos (mroos@...ux.ee)
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