linux-kernel - Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

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Message-ID: <20080828130708.GA19672@elte.hu>
Date:	Thu, 28 Aug 2008 15:07:08 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org,
	Stefani Seibold <stefani@...bold.net>,
	Dario Faggioli <raistlin@...ux.it>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

* Nick Piggin <nickpiggin@...oo.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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