linux-kernel - Re: sched_rt_period_timer causing large latencies

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Message-ID: <20180405082701.GL4082@hirez.programming.kicks-ass.net>
Date:   Thu, 5 Apr 2018 10:27:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: sched_rt_period_timer causing large latencies

On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote:
> Hi,
> 
> I'm seeing some pretty big latencies on a ~idle system when a CPU wakes
> out of a nohz idle. Looks like it's due to the taking a lot of remote
> locks and cache lines. irqoff trace:

On RT I think we default RT_RUNTIME_SHARE to false, maybe we should do
the same for mainline. It's always been a dodgy feature and if we ever
figure out how to do FIFO servers this code will be deleted entirely.