Nobody interested or it just slipped through? On Fri 05-08-11 13:42:21, Michal Hocko wrote: > [Added cpufreq people into CC - the email thread started at > https://lkml.org/lkml/2011/7/25/227] > > This patch set aims at addressing /proc/stat issue which has been > introduced with tickless kernel. > In short, show_stat (proc handler) relies on kstat_cpu(i).cpustat > statistics which are updated periodically so those numbers are more or > less accurate. > This is, however, not true with tickless kernel for idle and iowait > counters because those are not updated while the cpu is in the tickless > state. As the time when CPU might be tickless is not bounded, we can see > really outdated values. > The biggest problem is that tools which read /proc/stat interpret > unchanged idle/iowait numbers as 0% idle/iowait which might confuse > those who rely on them. > > First patch in this series changes update_ts_time_stat semantic. The > current implementation updates idle counter regardless we are in iowait > loop at the moment. I see it as an optimization because cpufreq drivers, > which are only users of those counters, care about busy vs. non-busy > states so idle+iowait makes perfect sense. This, however, makes idle > counter useless for others. > I think that calling using get_cpu_idle_time_us + get_cpu_iowait_time_us > should have the same meaning (at least this is what we do for jiffies > variants). > This is necessary for the third patch. > > The second patch is trivial and just a cleanup. It is not necessary for > the series but I fixed those macros while I was at it. > > The third patch uses get_cpu_{idle,iowait}_time_us to get precise > counters. We still fall back to kstat_cpu if tickless kernel is > disabled. > > Thanks for any comments. > > Michal Hocko (3): > tick: fix update_ts_time_stat idle accounting > cputime: clean up cputime_to_usecs and usecs_to_cputime macros > proc: consider NO_HZ when printing idle and iowait times > > drivers/cpufreq/cpufreq_conservative.c | 4 ++- > drivers/cpufreq/cpufreq_ondemand.c | 4 ++- > fs/proc/stat.c | 41 ++++++++++++++++++++++++++----- > include/asm-generic/cputime.h | 4 +- > kernel/time/tick-sched.c | 8 +++--- > 5 files changed, 46 insertions(+), 15 deletions(-) > > -- > 1.7.5.4 -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
