On 3/18/21 1:22 AM, Daniel Jordan wrote:
Andrey Ryabinin arbn@yandex-team.com 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