On Fri, 2007-07-20 at 09:22 +0200, Ingo Molnar wrote: > * Paul Mackerras <[EMAIL PROTECTED]> wrote: > > As with s390, 64-bit PowerPC also uses CONFIG_VIRT_CPU_ACCOUNTING. > > That affects how tsk->utime and tsk->stime are accumulated (we call > > account_user_time and account_system_time directly rather than calling > > update_process_times) as well as the system hardirq/softirq time, idle > > time, and stolen time. > > tsk->utime and tsk->stime is only used for a single purpose: to > determine the 'split' factor of how to split up the precise total time > between user and system time. > > > When you say "precise task statistics for /proc", where are they > > accumulated? I don't see any changes to the way that tsk->utime and > > ctime are computed. > > we now use p->se.sum_exec_runtime that measures (in nanoseconds) the > precise amount of time spent executing (sum of system and user time) - > and ->stime and ->utime is used to determine the 'split'. [this allows > us to gather ->stime and ->utime via low-resolution sampling, while > keeping the 'total' precise. Accounting at every system entry point > would be quite expensive on most platforms.]
Using se.sum_exec_runtime to generate ->utime and ->stime breaks the process accounting we have on s390 (and probably on PowerPC too). With CONFIG_VIRT_CPU_ACCOUNTING we already have precise values in ->utime and ->stime. Can we make the calculation of the CFS-based time values conditional by CONFIG_VIRT_CPU_ACCOUNTING? Jan > Ingo > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
