Date: Mon, 29 Nov 2004 16:57:52 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Esben Nielsen <simlo@phys.au.dk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Priority Inheritance Test (Real-Time Preemption)
Message-ID: <20041129155752.GA17828@elte.hu>
References: <20041129095941.GD7868@elte.hu> <Pine.OSF.4.05.10411291152050.14592-100000@da410.ifa.au.dk> <20041129155642.GA17663@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> > iteration over a list which can be O(number of waiters * locking
> > depth) long. As long as we are in the kernel both is "controlled",
> > i.e. one can see the worst-case number in stress test and know it
> > can't get worse. *
> 
> which list do you mean? Note that the pi_list depends on the number of
> _RT-tasks_, not on the number of SCHED_NORMAL tasks. So you can create
> an arbitrary number of SCHED_NORMAL tasks, they wont impact the
> overhead of mutexes!
> 
> i very intentionally made it independent of nr-of-non-RT-tasks.

and i'm regularly testing this property with 'hackbench 50', which
creates over a 1000 wildly scheduling non-RT tasks. Latency is not
affected by such workloads.

	Ingo
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