From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Clark Williams <williams@redhat.com>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC][PATCH] sched/rt: Use IPI to trigger RT task push migration instead of pulling
Date: Fri, 06 Feb 2015 16:58:08 +0100 [thread overview]
Message-ID: <1423238288.3377.83.camel@gmail.com> (raw)
In-Reply-To: <20150206124051.GN21418@twins.programming.kicks-ass.net>
On Fri, 2015-02-06 at 13:40 +0100, Peter Zijlstra wrote:
> On Thu, Feb 05, 2015 at 11:04:20AM -0500, Steven Rostedt wrote:
> Well, the thing is, with or without this patch, the worst case is still
> the very same. The likelihood of actually triggering it goes down
> dramatically [*], but any spin_lock() has that O(nr_cpus) worst case, and
> that spinlock op isn't going away.
>
> Now, lowering avg/median cases is good, but don't kid yourself that the
> worst case is going to be better.
>
> People running -RT on big boxes had better be aware of this.
The folks I know of running -RT on big boxen isolate cores and nail
absolutely everything to the floor. The only way to survive in a big
box is to chop the thing into tiny pieces. A plasma cutter would be
even better.. 'course you could just _buy smaller boxen_ and connect
what you want connected, take the lazy path to big box solution ;-)
-Mike
next prev parent reply other threads:[~2015-02-06 15:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-04 19:39 [RFC][PATCH] sched/rt: Use IPI to trigger RT task push migration instead of pulling Steven Rostedt
2015-02-05 14:58 ` Peter Zijlstra
2015-02-05 16:04 ` Steven Rostedt
2015-02-06 12:40 ` Peter Zijlstra
2015-02-06 15:58 ` Mike Galbraith [this message]
2015-02-05 15:21 ` Peter Zijlstra
2015-02-05 16:55 ` Steven Rostedt
2015-02-06 13:23 ` Peter Zijlstra
2015-02-06 13:59 ` Peter Zijlstra
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