Commit ccdec921 authored by Xuewen Yan's avatar Xuewen Yan Committed by Tejun Heo
Browse files

workqueue: Control intensive warning threshold through cmdline 



When CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel will report
the work functions which violate the intensive_threshold_us repeatedly.
And now, only when the violate times exceed 4 and is a power of 2,
the kernel warning could be triggered.

However, sometimes, even if a long work execution time occurs only once,
it may cause other work to be delayed for a long time. This may also
cause some problems sometimes.

In order to freely control the threshold of warninging, a boot argument
is added so that the user can control the warning threshold to be printed.
At the same time, keep the exponential backoff to prevent reporting too much.

By default, the warning threshold is 4.

tj: Updated kernel-parameters.txt description.

Signed-off-by: default avatarXuewen Yan <xuewen.yan@unisoc.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent bccdc1fa

Documentation/admin-guide/kernel-parameters.txt

+9 −0
Original line number Diff line number Diff line
@@ -7219,6 +7219,15 @@ 
			threshold repeatedly. They are likely good

			candidates for using WQ_UNBOUND workqueues instead.



	workqueue.cpu_intensive_warning_thresh=<uint>

			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel

			will report the work functions which violate the

			intensive_threshold_us repeatedly. In order to prevent

			spurious warnings, start printing only after a work

			function has violated this threshold number of times.



			The default is 4 times. 0 disables the warning.



	workqueue.power_efficient

			Per-cpu workqueues are generally preferred because

			they show better performance thanks to cache

kernel/workqueue.c

+11 −3
Original line number Diff line number Diff line
@@ -409,6 +409,10 @@ static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = { 
 */

static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;

module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);

#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT

static unsigned int wq_cpu_intensive_warning_thresh = 4;

module_param_named(cpu_intensive_warning_thresh, wq_cpu_intensive_warning_thresh, uint, 0644);

#endif



/* see the comment above the definition of WQ_POWER_EFFICIENT */

static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
@@ -1327,11 +1331,13 @@ static void wq_cpu_intensive_report(work_func_t func) 
		u64 cnt;



		/*

		 * Start reporting from the fourth time and back off

		 * Start reporting from the warning_thresh and back off

		 * exponentially.

		 */

		cnt = atomic64_inc_return_relaxed(&ent->cnt);

		if (cnt >= 4 && is_power_of_2(cnt))

		if (wq_cpu_intensive_warning_thresh &&

		    cnt >= wq_cpu_intensive_warning_thresh &&

		    is_power_of_2(cnt + 1 - wq_cpu_intensive_warning_thresh))

			printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",

					ent->func, wq_cpu_intensive_thresh_us,

					atomic64_read(&ent->cnt));
@@ -1360,10 +1366,12 @@ static void wq_cpu_intensive_report(work_func_t func) 


	ent = &wci_ents[wci_nr_ents++];

	ent->func = func;

	atomic64_set(&ent->cnt, 1);

	atomic64_set(&ent->cnt, 0);

	hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);



	raw_spin_unlock(&wci_lock);



	goto restart;

}



#else	/* CONFIG_WQ_CPU_INTENSIVE_REPORT */