linux-kernel - Re: [PATCH] sched/rt: don't try to balance rt

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Message-ID: <20140519105404.GZ30445@twins.programming.kicks-ass.net>
Date:	Mon, 19 May 2014 12:54:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	paulmck@...ux.vnet.ibm.com,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] sched/rt: don't try to balance rt_runtime when it is
 futile

On Thu, May 15, 2014 at 05:18:51AM +0200, Mike Galbraith wrote:
> On Wed, 2014-05-14 at 08:44 -0700, Paul E. McKenney wrote:
> 
> > In practice, not sure how much testing CONFIG_NO_HZ_FULL=y has received
> > for -rt kernels in production environments.
> 
> I took 3.14-rt out for a quick spin on my 64 core box, it didn't work at
> all with 60 cores isolated.  I didn't have time to rummage, but it looks
> like there are still bugs to squash. 
> 
> Biggest problem with CONFIG_NO_HZ_FULL is the price tag.  It just raped
> fast mover performance last time I measured.

Syscall entry and exit times are through the roof with it. So anything
doing loads of syscalls will suffer badly.

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