Hi, On 05/20/2013 09:40 AM, Ola Liljedahl wrote:
In my experience, networking is moving away from realtime scheduling (and thus RTOS’es). There are some lingering requirements for some of the processing in the wireless stack but the main difficulty here is getting the scheduling latency down to acceptable levels, e.g. five microseconds or so. Will SCHED_DEADLINE help here?
No, SCHED_DEADLINE isn't about reducing latency. That is instead the job of the PREEMPT_RT patchset. However, EDF scheduling is useful to control and reduce response time (and this can be seen as some sort of latency). Best, - Juri
-- Ola *Ola Liljedahl, Networking System Architect, ARM* *Telephone: +46 706 866 373 Skype: ola.liljedahl* *From:*Amit Kucheria [mailto:amit.kuche...@linaro.org] *Sent:* 19 May 2013 11:51 *To:* Mark Orvek *Cc:* Patrick MacCartee; Mike Holmes; linaro-networking; Lists linaro-dev; j.le...@sssup.it; linaro-enterpr...@linaro.org; lng...@linaro.org *Subject:* Re: Deadline scheduler inclusion in linux-linaro? Similarly, the SCHED_DEADLINE patches shouldn't affect default runtime scheduler behaviour unless a task uses the DEADLINE policy. However, I haven't studied the intersection of the Preempt RT and SCHED_DEADLINE patches in source form yet. If they touch common pieces of code, merging both in might be an ongoing effort. Juri, do you know? On Fri, May 17, 2013 at 8:11 PM, Mark Orvek <mark.or...@linaro.org <mailto:mark.or...@linaro.org>> wrote: The PREEMPT_RT patchset is configurable. I believe the default is PREEMPT_DESKTOP which is what most MV CGE customers use. Another config options is PREEMPT_NONE but I believe its usage is rare. Mark On Fri, May 17, 2013 at 7:25 AM, Patrick MacCartee <pmaccar...@mvista.com <mailto:pmaccar...@mvista.com>> wrote: Will these be added in a way that makes them easy to remove? Many, >95% don't use Preempt RT in Linux as it impacts network performance and makes things very temperamental. You would think people would just disable this RT, but when trying to isolate issues it adds another variable to the mix. I believe Yocto has a way of adding and removing RT patches that is some what straight forward and preferable based on feedback from OEM's. Just a thought, Patrick On Fri, May 17, 2013 at 6:34 AM, Mike Holmes <mike.hol...@linaro.org <mailto:mike.hol...@linaro.org>> wrote: In LNG you could end up with an interesting mix of preempt RT and deadline patches making the analysis and benchmarking interesting to interpret. In addition there are discussions about adding zero overhead linux (ZOL) like features. Mike On Friday, May 17, 2013 6:08:20 AM UTC-4, David Rusling wrote: Amit, an interesting proposal. I think that most of the LNG steering committee is on this alias, but just in case, I'm adding them to it... Dave Amit Kucheria 17 May 2013 10:15 Hi all, As part of our investigations into the Linux scheduler we've interacted with Juri Lelli at the University of Pisa (cc'ed) who is part of a group that is working on a DEADLINE scheduler[1] for Linux[2]. While we're coming at this from a power managment angle[3], I suspect that LEG and LNG already have real-world usecases that would benefit from deadline scheduler found in other RTOSes. So I think it makes sense to merge Juri's tree into linux-linaro going forward to allow easier experimentation. Does LEG and LNG have any interest in this at this point? Juri has expressed an interest in maintaining a current branch of the code that could be merged into our monthly release. In return, real world usecases will improve his chances of getting the code merged into mainline. Regards, Amit [1] http://retis.sssup.it/?q=node/35 [2] https://lkml.org/lkml/2013/2/11/373 [3] Mostly involving discussions at this point, no real engineering effort invested yet _______________________________________________ linaro-dev mailing list linar...@lists.linaro.org <mailto:linar...@lists.linaro.org> http://lists.linaro.org/mailman/listinfo/linaro-dev -- David Rusling CTO Linaro Ltd e. david....@linaro.org <mailto:david....@linaro.org> w. http://www.linaro.org Linaro: The future of Linux on ARM -- Patrick J. MacCartee Director of Product Management MontaVista Software LLC fone: 408-572-7937 <tel:408-572-7937> mobile: 415-637-0257 <tel:415-637-0257> pmaccar...@mvista.com <mailto:pmaccar...@mvista.com> -- Mark Orvek mark.or...@linaro.org <mailto:mark.or...@linaro.org> VP, Engineering *M*: +1.408.313.6988*IRC:* morvek *Skype:* morvek linaro.org <http://linaro.org> │ Open source software for ARM SoCs -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
_______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
