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SubjectRe: [PATCH 8/9] per-cgroup boot time
On 09/20/2011 06:25 AM, Peter Zijlstra wrote:
> On Wed, 2011-09-14 at 17:04 -0300, Glauber Costa wrote:
>> Record the time in which the cgroup was created. This can be
>> used to provide a more accurate boottime information in
>> cpuacct.proc.stat.
>>
>> Signed-off-by: Glauber Costa<glommer@parallels.com>
>> ---
>> kernel/sched.c | 8 +++++++-
>> 1 files changed, 7 insertions(+), 1 deletions(-)
>>
>> diff --git a/kernel/sched.c b/kernel/sched.c
>> index 4611c54..8f254d0 100644
>> --- a/kernel/sched.c
>> +++ b/kernel/sched.c
>> @@ -9120,6 +9120,7 @@ struct cpuacct {
>> /* cpuusage holds pointer to a u64-type object on every cpu */
>> u64 __percpu *cpuusage;
>> u64 __percpu *cpustat;
>> + struct timespec start_time;
>> };
>>
>> struct cgroup_subsys cpuacct_subsys;
>> @@ -9172,6 +9173,8 @@ static struct cgroup_subsys_state *cpuacct_create(
>> acct[CPUACCT_STAT_IDLE] = kstat_cpu(i).cpustat.idle;
>> acct[CPUACCT_STAT_IOWAIT] = kstat_cpu(i).cpustat.iowait;
>> }
>> +
>> + get_monotonic_boottime(&ca->start_time);
>> return&ca->css;
>>
>> out_free_usage:
>> @@ -9316,13 +9319,16 @@ static int cpuacct_proc_stat(struct cgroup *cgrp, struct cftype *cft,
>> unsigned int per_softirq_sums[NR_SOFTIRQS] = {0};
>> struct timespec boottime;
>> struct cpuacct *ca = cgroup_ca(cgrp);
>> + struct timespec ts;
>> u64 *cpustat;
>>
>> user = nice = system = idle = iowait =
>> irq = softirq = steal = cputime64_zero;
>> guest = guest_nice = cputime64_zero;
>> getboottime(&boottime);
>> - jif = boottime.tv_sec;
>> + getboottime(&boottime);
>> + ts = timespec_add(boottime, ca->start_time);
>> + jif = ts.tv_sec;
>>
>> for_each_possible_cpu(i) {
>> cpustat = per_cpu_ptr(ca->cpustat, i);
>
>
> I'm confused, what does it do? You take a boot time timestamp at cgroup
> creation, add that to all boot-time readings and print the result. How
> does that make sense? Subtracting the start_time, maybe, that would make
> the cgroup creation time 0, adding, not so much.

Boot time represent at which times the machine was booted. In this
context, at which time the container/cgroup was created. So it have to
be an addition.... don't really understand your question


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