On Thu, Apr 11, 2013 at 08:22:03PM +0200, Frederic Weisbecker wrote: > On Thu, Apr 11, 2013 at 08:07:50PM +0200, Peter Zijlstra wrote: > > On Thu, 2013-04-11 at 08:38 -0700, Linus Torvalds wrote: > > > On Thu, Apr 11, 2013 at 6:45 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > On Tue, 2013-03-26 at 15:01 +0100, Stanislaw Gruszka wrote: > > > >> Thoughts? > > > > > > > > Would something like the below work? > > > > > > Ugh, this is hard to think about, it's also fairly inefficient. > > > > > > > static cputime_t scale_stime(u64 stime, u64 rtime, u64 total) > > > > { > > > > - u64 rem, res, scaled; > > > > + int stime_fls = fls64(stime); > > > > + int total_fls = fls64(total); > > > > + int rtime_fls = fls64(rtime); > > > > > > Doing "fls64()" unconditionally is quite expensive on some > > > architectures, > > > > Oh, I (wrongly it appears) assumed that fls was something cheap :/ > > > > > and if I am not mistaken, the *common* case (by far) is > > > that all these values fit in 32 bits, no? > > > > It depends on if we use cputime_jiffies.h or cputime_nsec.h and I'm > > completely lost as to which we default to atm. But we sure can reduce > > to 32 bits in most cases without too much problems. > > We default to the jiffies. The nsecs case is used only for full dynticks > accounting and ia64 precise accounting. Oh and in the latter case there is no scaling. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html