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Date: Sun, 21 Nov 2010 09:37:16 +0100 From: Rodolfo Giometti <giometti@...eenne.com> To: Alexander Gordeev <lasaine@....cs.msu.su> Cc: linux-kernel@...r.kernel.org, "Nikita V. Youshchenko" <yoush@...msu.su>, linuxpps@...enneenne.com, Andrew Morton <akpm@...ux-foundation.org>, Tejun Heo <tj@...nel.org> Subject: Re: [PATCHv4 08/17] pps: add async PPS event handler On Sun, Nov 21, 2010 at 02:23:02AM +0300, Alexander Gordeev wrote: > ?? Sat, 20 Nov 2010 17:08:51 +0100 > Rodolfo Giometti <giometti@...eenne.com> ??????????: > > > On Thu, Nov 18, 2010 at 07:01:01PM +0300, Alexander Gordeev wrote: > > > This handler should be called from an IRQ handler. It uses per-device > > > workqueue internally. > > > > Can you please explain to me why do you need this patch? Maybe you can > > add a verbose patch's description? :) > > Well, it's all about optimizing latencies on rt-preempt kernel: if > everything is done in a process context than we can use mutexes > (haven't done that yet) and don't disable interrupts, which is better > for hard real time. I measured that pps_event with kernel consumer > enabled takes 1-2us on my test machine. Not a big deal, of course... > > Sorry, I've completely forgotten about an echo function. However quick > look to current clients shows that it is only used in pps-ktimer.c > for debug printing... Maybe it's not needed at all? I mean, have you > ever got any user request for this feature? If yes, it can be removed > IMHO since RFC-2783 says that it's optional. I can handle the removal in > the next version of the patchset. > > If you don't want it I can have this patch on my rt branch only and > don't try to push it into mainline. The echo function is not used as far as I know, so it's ok for me to remove echo support if you get better performance. In case we can study how to reimplement it! ;) Acked-by: Rodolfo Giometti <giometti@...ux.it> -- GNU/Linux Solutions e-mail: giometti@...eenne.com Linux Device Driver giometti@...ux.it Embedded Systems phone: +39 349 2432127 UNIX programming skype: rodolfo.giometti Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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