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Date: Fri, 22 Oct 2010 10:28:30 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Bruno Randolf <br1@...fach.org> Cc: kosaki.motohiro@...fujitsu.com, randy.dunlap@...cle.com, akpm@...ux-foundation.org, kevin.granade@...il.com, Lars_Ericsson@...ia.com, blp@...stanford.edu, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3] Add generic exponentially weighted moving average (EWMA) function > On Fri October 22 2010 10:11:38 KOSAKI Motohiro wrote: > > few additional reviewing comments is here. > > > > > +struct ewma { > > > + unsigned int internal; > > > + unsigned int factor; > > > + unsigned int weight; > > > +}; > > > > I think unsigned long is better because long is natual register size > > on both 32bit and 64bit arch. > > and, example, almost linux resource limit is using long or ulong. then > > uint may have overflow risk if we are using this one on 64bit arch. > > Does uint has any benefit? (note: scheduler loadavg has already used ulong) > > You know more about this than me. I have no specific reason to use unsigned > int. I'll change it to unsigned long, if that's better. Thank you. > > > +struct ewma* > > > +ewma_add(struct ewma *avg, const unsigned int val) > > > +{ > > > + avg->internal = avg->internal ? > > > + (((avg->internal * (avg->weight - 1)) + > > > + (val * avg->factor)) / avg->weight) : > > > + (val * avg->factor); > > > + return avg; > > > > Hm, if ewma_add has this function prototype, we almost always need to > > typing "new = ewma_get(ewma_add(&ewma, val))". Is this intentional? > > if so, why? > > > > Why can't we simple do following? > > > > unsigned long ewma_add(struct ewma *avg, const unsigned int val) > > { > > (snip) > > return ewma_get(avg); > > } > > Hmm, I guess that depends on the way you want to use it. In my case, most of > the times when I add a value to the average, I don't need to get the value. > I'd call ewma_add() many more times than ewma_get(). Having the functions > defined like this gives us the flexibility to choose and IMHO > ewma_get(ewma_add(&ewma, val)) isn't so bad? OK. I've got it. I agree we don't change this. Thank you for very quick responce! -- 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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