Re: [PATCH v1] PM: sleep: Restore asynchronous device resume optimization

Tejun Heo
2024-02-07T19:48:39Z

Hello,

I couldn't reproduce effective max_active being pushed down to min_active
across suspend/resume cycles on x86. There gotta be something different.

- Can you please apply the following patch along with the WQ_DFL_MIN_ACTIVE
bump, go through suspend/resume once and report the dmesg?

- Regardless of the root cause, I think async should switch to a dedicated
workqueue with explicitly raised min_active (will add an interface for
it).

Thanks.

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cf514ba0dfc3..93e5b837f2b4 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -368,6 +368,8 @@ struct workqueue_struct {
*/
struct rcu_head rcu;

+ bool dbg;
+
/* hot fields used during command issue, aligned to cacheline */
unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
@@ -1557,6 +1559,10 @@ static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
if (off_cpu >= 0)
total_cpus--;

+ if (wq->dbg)
+ printk("XXX wq_update_node_max_active: wq=%s off_cpu=%d total=%d range=[%d, %d]",
+ wq->name, off_cpu, total_cpus, min_active, max_active);
+
for_each_node(node) {
int node_cpus;

@@ -1567,7 +1573,12 @@ static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
wq_node_nr_active(wq, node)->max =
clamp(DIV_ROUND_UP(max_active * node_cpus, total_cpus),
min_active, max_active);
+ if (wq->dbg)
+ pr_cont(" node[%d] node_cpus=%d max=%d",
+ node, node_cpus, wq_node_nr_active(wq, node)->max);
}
+ if (wq->dbg)
+ pr_cont("\n");

wq_node_nr_active(wq, NUMA_NO_NODE)->max = min_active;
}
@@ -4886,6 +4897,9 @@ static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,

old_pwq = rcu_access_pointer(*slot);
rcu_assign_pointer(*slot, pwq);
+ if (wq->dbg)
+ printk("XXX install_unbound_pwq: wq=%s cpu=%d pool=%d\n",
+ wq->name, cpu, pwq->pool->id);
return old_pwq;
}

@@ -7418,6 +7432,8 @@ void __init workqueue_init_early(void)
!system_power_efficient_wq ||
!system_freezable_power_efficient_wq ||
!system_bh_wq || !system_bh_highpri_wq);
+
+ system_unbound_wq->dbg = true;
}

static void __init wq_cpu_intensive_thresh_init(void)