From: Ingo Molnar <mingo@elte.hu>
To: Esben Nielsen <simlo@phys.au.dk>
Cc: Gabor MICSKO <gmicsko@szintezis.hu>, linux-kernel@vger.kernel.org
Subject: Re: hackbench: 2.6.12-rc6 vs. 2.6.12-rc6-RT-V0.7.48-06
Date: Sat, 11 Jun 2005 06:32:31 +0200 [thread overview]
Message-ID: <20050611043231.GA16500@elte.hu> (raw)
In-Reply-To: <Pine.OSF.4.05.10506102306360.5042-100000@da410.phys.au.dk>
* Esben Nielsen <simlo@phys.au.dk> wrote:
> Depends on the configuration options. If you used the same configs
> they should be the same but if you activated PREEMPT_RT it should slow
> things down due to the overhead of irq-threading and mutexes instead
> of spinlocks - although I am surprised the factor is _that_ big!
one has to make sure the default debug options are disabled.
(DEADLOCK_DETECT, PREEMPT_DEBUG, etc.) But even then there will be
considerable overhead. Until recently, the overhead used to be even
bigger. Note that hackbench is pretty much the worst-case for
PREEMPT_RT: lots of locking and scheduling done and we compare the UP
kernel to the SMP kernel in essence. (in fact PREEMPT_RT's locking is
currently higher overhead than SMP)
Ingo
prev parent reply other threads:[~2005-06-11 4:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-10 20:56 Gabor MICSKO
2005-06-10 21:09 ` Esben Nielsen
2005-06-11 4:32 ` Ingo Molnar [this message]
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