On 2022/8/24 17:59, Johannes Weiner wrote:
> Hi Chengming,
>
> Thanks for incorporating all the feedback. I have a few nitpicks
> below, but with those considered, please add:
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
>
> On Wed, Aug 24, 2022 at 04:18:29PM +0800, Chengming Zhou wrote:
>> @@ -5171,12 +5220,19 @@ static struct cftype cgroup_base_files[] = {
>> {
>> .name = "irq.pressure",
>> .flags = CFTYPE_PRESSURE,
>> + .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
>> .seq_show = cgroup_irq_pressure_show,
>> .write = cgroup_irq_pressure_write,
>> .poll = cgroup_pressure_poll,
>> .release = cgroup_pressure_release,
>> },
>> #endif
>> + {
>> + .name = "cgroup.pressure",
>> + .flags = CFTYPE_PRESSURE,
>> + .seq_show = cgroup_psi_show,
>> + .write = cgroup_psi_write,
>
> To match the naming convention, these should be called
> cgroup_pressure_show() and cgroup_pressure_write().
I just find cgroup_pressure_write() already exists, so I change the names
to cgroup_pressure_enable_show() and cgroup_pressure_enable_write(),
since this file name is simplified from "cgroup.pressure.enable".
Thanks.
>
>> @@ -745,6 +745,14 @@ static void psi_group_change(struct psi_group *group, int cpu,
>> if (set & (1 << t))
>> groupc->tasks[t]++;
>>
>> + if (!group->enabled) {
>> + if (groupc->state_mask & (1 << PSI_NONIDLE))
>> + record_times(groupc, now);
>
> Thanks for the explanation in the other thread, it made sense. But can
> you please add a comment to document it? Something like:
>
> /*
> * On the first group change after disabling PSI, conclude
> * the current state and flush its time. This is unlikely
> * to matter to the user, but aggregation (get_recent_times)
> * may have already incorporated the live state into times_prev;
> * avoid a delta sample underflow when PSI is later re-enabled.
> */
>
> An unlikely() would also make sense on that branch.
>
>> @@ -1081,6 +1092,40 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
>>
>> task_rq_unlock(rq, task, &rf);
>> }
>> +
>> +void psi_cgroup_enabled_sync(struct psi_group *group)
>> +{
>> + int cpu;
>> +
>> + /*
>> + * After we disable psi_group->enabled, we don't actually
>> + * stop percpu tasks accounting in each psi_group_cpu,
>> + * instead only stop test_state() loop, record_times()
>> + * and averaging worker, see psi_group_change() for details.
>> + *
>> + * When disable cgroup PSI, this function has nothing to sync
>> + * since cgroup pressure files are hidden and percpu psi_group_cpu
>> + * would see !psi_group->enabled and only do task accounting.
>> + *
>> + * When re-enable cgroup PSI, this function use psi_group_change()
>> + * to get correct state mask from test_state() loop on tasks[],
>> + * and restart groupc->state_start from now, use .clear = .set = 0
>> + * here since no task status really changed.
>> + */
>> + if (!group->enabled)
>> + return;
>
> Thanks for adding the comment, that's helpful.
>
> I think the function would be a tad clearer and self-documenting if
> you called it psi_cgroup_restart(), and only call it on enabling.
>
>> + for_each_possible_cpu(cpu) {
>> + struct rq *rq = cpu_rq(cpu);
>> + struct rq_flags rf;
>> + u64 now;
>> +
>> + rq_lock_irq(rq, &rf);
>> + now = cpu_clock(cpu);
>> + psi_group_change(group, cpu, 0, 0, now, true);
>> + rq_unlock_irq(rq, &rf);
>> + }
>> +}
>> #endif /* CONFIG_CGROUPS */
>
> Thanks,
> Johannes
