On 07/19, Peter Zijlstra wrote: > > > > $ ./stime 300000 > > > start=300000000000000 > > > ut(diff)/st(diff): 299994875 ( 0) 300009124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300011124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300013124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300015124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300017124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300019124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300021124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300023124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300025124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300027124 > > > (2000) > > > ut(diff)/st(diff): 299994875 ( 0) 300029124 > > > (2000) > > > ut(diff)/st(diff): 299996875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 299998875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300000875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300002875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300004875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300006875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300008875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300010875 (2000) 300029124 ( > > > 0) > > > ut(diff)/st(diff): 300012055 (1180) 300029944 ( > > > 820) > > > ut(diff)/st(diff): 300012055 ( 0) 300031944 > > > (2000) > > > ut(diff)/st(diff): 300012055 ( 0) 300033944 > > > (2000) > > > ut(diff)/st(diff): 300012055 ( 0) 300035944 > > > (2000) > > > ut(diff)/st(diff): 300012055 ( 0) 300037944 > > > (2000) > > > > > > shows the problem even when sum_exec_runtime is not that big: 300000 secs. > > > > > > The new implementation of scale_stime() does the additional > > > div64_u64_rem() > > > in a loop but see the comment, as long it is used by cputime_adjust() this > > > can happen only once. > > > > That only shows something after long long staring :/ There's no words on > > what the output actually means or what would've been expected. > > > > Also, your example is incomplete; the below is a test for scale_stime(); > > from this we can see that the division results in too large a number, > > but, important for our use-case in cputime_adjust(), it is a step > > function (due to loss in precision) and for every plateau we shift > > runtime into the wrong bucket. > > But I'm still confused, since in the long run, it should still end up > with a proportionally divided user/system, irrespective of some short > term wobblies.
Why? Yes, statistically the numbers are proportionally divided. but you will (probably) never see the real stime == 1000 && utime == 10000 numbers if you watch incrementally. Just in case... yes I know that these numbers can only "converge" to the reality, only their sum is correct. But people complain. Oleg.
