On 3/18/21 1:22 AM, Daniel Jordan wrote: > Andrey Ryabinin <arbn@xxxxxxxxxxxxxxx> writes: > >> cpuacct has 2 different ways of accounting and showing user >> and system times. >> >> The first one uses cpuacct_account_field() to account times >> and cpuacct.stat file to expose them. And this one seems to work ok. >> >> The second one is uses cpuacct_charge() function for accounting and >> set of cpuacct.usage* files to show times. Despite some attempts to >> fix it in the past it still doesn't work. E.g. while running KVM >> guest the cpuacct_charge() accounts most of the guest time as >> system time. This doesn't match with user&system times shown in >> cpuacct.stat or proc/<pid>/stat. > > I couldn't reproduce this running a cpu bound load in a kvm guest on a > nohz_full cpu on 5.11. The time is almost entirely in cpuacct.usage and > _user, while _sys stays low. > > Could you say more about how you're seeing this? Don't really doubt > there's a problem, just wondering what you're doing. > Yeah, I it's almost unnoticable if you run some load in guest like qemu. But more simple case with busy loop in KVM_RUN triggers this: # git clone https://github.com/aryabinin/kvmsample # make # mkdir /sys/fs/cgroup/cpuacct/test # echo $$ > /sys/fs/cgroup/cpuacct/test/tasks # ./kvmsample & # for i in {1..5}; do cat /sys/fs/cgroup/cpuacct/test/cpuacct.usage_sys; sleep 1; done 1976535645 2979839428 3979832704 4983603153 5983604157 >> diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c >> index 941c28cf9738..7eff79faab0d 100644 >> --- a/kernel/sched/cpuacct.c >> +++ b/kernel/sched/cpuacct.c >> @@ -29,7 +29,7 @@ struct cpuacct_usage { >> struct cpuacct { >> struct cgroup_subsys_state css; >> /* cpuusage holds pointer to a u64-type object on every CPU */ >> - struct cpuacct_usage __percpu *cpuusage; > > Definition of struct cpuacct_usage can go away now. > Done. >> @@ -99,7 +99,8 @@ static void cpuacct_css_free(struct cgroup_subsys_state *css) >> static u64 cpuacct_cpuusage_read(struct cpuacct *ca, int cpu, >> enum cpuacct_stat_index index) >> { >> - struct cpuacct_usage *cpuusage = per_cpu_ptr(ca->cpuusage, cpu); >> + u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu); >> + u64 *cpustat = per_cpu_ptr(ca->cpustat, cpu)->cpustat; >> u64 data; > > There's a BUG_ON below this that could probably be WARN_ON_ONCE while > you're here > Sure. >> @@ -278,8 +274,8 @@ static int cpuacct_stats_show(struct seq_file *sf, void *v) >> for_each_possible_cpu(cpu) { >> u64 *cpustat = per_cpu_ptr(ca->cpustat, cpu)->cpustat; >> >> - val[CPUACCT_STAT_USER] += cpustat[CPUTIME_USER]; >> - val[CPUACCT_STAT_USER] += cpustat[CPUTIME_NICE]; >> + val[CPUACCT_STAT_USER] += cpustat[CPUTIME_USER]; >> + val[CPUACCT_STAT_USER] += cpustat[CPUTIME_NICE]; > > unnecessary whitespace change? > yup
