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-rw-r--r--kernel/workqueue.c43
1 files changed, 42 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 02a8f402eeb5..800b4208dba9 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -52,6 +52,7 @@
#include <linux/sched/debug.h>
#include <linux/nmi.h>
#include <linux/kvm_para.h>
+#include <linux/delay.h>
#include "workqueue_internal.h"
@@ -338,8 +339,10 @@ static cpumask_var_t *wq_numa_possible_cpumask;
* Per-cpu work items which run for longer than the following threshold are
* automatically considered CPU intensive and excluded from concurrency
* management to prevent them from noticeably delaying other per-cpu work items.
+ * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
+ * The actual value is initialized in wq_cpu_intensive_thresh_init().
*/
-static unsigned long wq_cpu_intensive_thresh_us = 10000;
+static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
static bool wq_disable_numa;
@@ -6513,6 +6516,42 @@ void __init workqueue_init_early(void)
!system_freezable_power_efficient_wq);
}
+static void __init wq_cpu_intensive_thresh_init(void)
+{
+ unsigned long thresh;
+ unsigned long bogo;
+
+ /* if the user set it to a specific value, keep it */
+ if (wq_cpu_intensive_thresh_us != ULONG_MAX)
+ return;
+
+ /*
+ * The default of 10ms is derived from the fact that most modern (as of
+ * 2023) processors can do a lot in 10ms and that it's just below what
+ * most consider human-perceivable. However, the kernel also runs on a
+ * lot slower CPUs including microcontrollers where the threshold is way
+ * too low.
+ *
+ * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
+ * This is by no means accurate but it doesn't have to be. The mechanism
+ * is still useful even when the threshold is fully scaled up. Also, as
+ * the reports would usually be applicable to everyone, some machines
+ * operating on longer thresholds won't significantly diminish their
+ * usefulness.
+ */
+ thresh = 10 * USEC_PER_MSEC;
+
+ /* see init/calibrate.c for lpj -> BogoMIPS calculation */
+ bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
+ if (bogo < 4000)
+ thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
+
+ pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
+ loops_per_jiffy, bogo, thresh);
+
+ wq_cpu_intensive_thresh_us = thresh;
+}
+
/**
* workqueue_init - bring workqueue subsystem fully online
*
@@ -6528,6 +6567,8 @@ void __init workqueue_init(void)
struct worker_pool *pool;
int cpu, bkt;
+ wq_cpu_intensive_thresh_init();
+
/*
* It'd be simpler to initialize NUMA in workqueue_init_early() but
* CPU to node mapping may not be available that early on some