Messages in this thread | | | Date | Sun, 12 Jun 2005 00:31:17 -0400 | From | Karim Yaghmour <> | Subject | Re: [PATCH] local_irq_disable removal |
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Daniel Walker wrote: > Interesting .. So "cli" takes 7 cycles , "sti" takes 7 cycles. The current > method does "lea" which takes 1 cycle, and "or" which takes 1 cycle. I'm > not sure if there is any function call overhead .. So the soft replacment > of cli/sti is 70% faster on a per instruction level .. So it's at least > not any slower .. Does everyone agree on that?
The proof is in the pudding: it's not for nothing that the results we published earlier show that the mere enabling of Adeos actually increases Linux's performance under heavy load.
This could easily be called the Stodolsky effect. Here, have a look at this article, it was presented at the USENIX Symposium on Microkernels and Other Kernel Architectures ... in 1993: http://www-2.cs.cmu.edu/afs/cs.cmu.edu/user/danner/www/OptSynch.ps We've been referring back to this paper as early as the first public release of Adeos ... in June 2002.
That being said, I'm not sure exactly why you guys are reinventing the wheel. Adeos already does this soft-cli/sti stuff for you, it's been available for a few years already, tested, and ported to a number of architectures, and is generalized, why not just adopt it? After all, like I've been saying for some time, it isn't mutually exclusive with PREEMPT_RT.
Karim -- Author, Speaker, Developer, Consultant Pushing Embedded and Real-Time Linux Systems Beyond the Limits http://www.opersys.com || karim@opersys.com || 1-866-677-4546 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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