Messages in this thread | | | Date | Sat, 16 Jul 2005 17:44:27 -0700 | From | Nishanth Aravamudan <> | Subject | Re: [RFC][PATCH 1/4] add jiffies_to_nsecs() helper and fix up size of usecs |
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On 15.07.2005 [14:14:25 +0200], Pavel Machek wrote: > Hi! > > > > > +static inline u64 jiffies_to_nsecs(const unsigned long j) > > > > +{ > > > > +#if HZ <= NSEC_PER_SEC && !(NSEC_PER_SEC % HZ) > > > > + return (NSEC_PER_SEC / HZ) * (u64)j; > > > > +#elif HZ > NSEC_PER_SEC && !(HZ % NSEC_PER_SEC) > > > > + return ((u64)j + (HZ / NSEC_PER_SEC) - 1)/(HZ / NSEC_PER_SEC); > > > > +#else > > > > + return ((u64)j * NSEC_PER_SEC) / HZ; > > > > +#endif > > > > +} > > > > > > That might look a little better something like: > > > > > > static inline u64 jiffies_to_nsecs(const unsigned long __j) > > > { > > > u64 j = __j; > > > > > > if (HZ <= NSEC_PER_SEC && !(NSEC_PER_SEC % HZ)) > > > return (NSEC_PER_SEC / HZ) * j; > > > else if (HZ > NSEC_PER_SEC && !(HZ % NSEC_PER_SEC)) > > > return (j + (HZ / NSEC_PER_SEC) - 1)/(HZ / NSEC_PER_SEC); > > > else > > > return (j * NSEC_PER_SEC) / HZ; > > > } > > > > > > Compilers are smart :) > > > > Well, I was trying to keep it similar to the other conversion functions. > > I guess the compiler can evaluate the conditional full of constants at > > compile-time regardless of whether it is #if or if (). > > > > I can make these changes if others would like them as well. > > Yes, please. And feel free to convert nearby functions, too ;-).
I have a patch to make this change for all the jiffies <--> human-time functions, but have a problem. I noticed that these functions, in the if/else form (as opposed to #if/#else) will warn about division-by-zero problems, as (HZ / MSEC_PER_SEC), (HZ / USEC_PER_SEC) & (HZ / NSEC_PER_SEC) are all 0 if HZ < 1000 (which, of course, is the default now :) ). Any suggestions? Just leave the functions as is? Even then, I'm going to update this patch to use USEC_PER_SEC and MSEC_PER_SEC in the other conversion functions like I use NSEC_PER_SEC in the first version.
Thanks, Nish - 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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