Date: Thu, 28 Aug 2008 15:07:08 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andi Kleen <andi@firstfloor.org>, Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org,
       Stefani Seibold <stefani@seibold.net>,
       Dario Faggioli <raistlin@linux.it>, Max Krasnyansky <maxk@qualcomm.com>,
       Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 6/6] sched: disabled rt-bandwidth by default
Message-ID: <20080828130708.GA19672@elte.hu>
References: <20080819103301.787700742@chello.nl> <200808272008.16106.nickpiggin@yahoo.com.au> <20080828105408.GA4488@elte.hu> <200808282203.48396.nickpiggin@yahoo.com.au>
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* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> There is no customer issue and there is no handwaving about 
> compliance;

well, the reason i'm asking is that i cannot for anything in the world 
imagine you being so upset about _anything_ but something that involves 
benchmark runs ;-)

And what does SCHED_FIFO RT policy scheduling have to do with 
performance and benchmarks? Nothing usually in the real world, except 
for this little known fact: a common 'tuning' for TPC database 
benchmarks is to run all DB threads as SCHED_FIFO to squeeze the last 
0.1% of performance out of the setup.

So - and i'm taking an educated guess here - is SCHED_FIFO+TPC 
performance perhaps one of the factors that played a role in you 
initiating this thread? If yes then it's obviously an incredibly broken 
use of SCHED_FIFO and we can add the sysctl tuning to the long list of 
dozens of other tunings that happen before a TPC run anyway.

Hm?

	Ingo
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