Messages in this thread Patch in this message | | | Date | Wed, 24 Aug 2022 05:59:40 -0400 | From | Johannes Weiner <> | Subject | Re: [PATCH v3 10/10] sched/psi: per-cgroup PSI accounting disable/re-enable interface |
| |
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@cmpxchg.org>
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().
> @@ -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
| |