* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
+ *
+ * See Documentation/slow-work.txt
*/
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/wait.h>
-#include <asm/system.h>
+
+#define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of
+ * things to do */
+#define SLOW_WORK_OOM_TIMEOUT (5 * HZ) /* can't start new threads for 5s after
+ * OOM */
+
+static void slow_work_cull_timeout(unsigned long);
+static void slow_work_oom_timeout(unsigned long);
+
+#ifdef CONFIG_SYSCTL
+static int slow_work_min_threads_sysctl(struct ctl_table *, int, struct file *,
+ void __user *, size_t *, loff_t *);
+
+static int slow_work_max_threads_sysctl(struct ctl_table *, int , struct file *,
+ void __user *, size_t *, loff_t *);
+#endif
/*
* The pool of threads has at least min threads in it as long as someone is
static unsigned slow_work_max_threads = 4;
static unsigned vslow_work_proportion = 50; /* % of threads that may process
* very slow work */
+
+#ifdef CONFIG_SYSCTL
+static const int slow_work_min_min_threads = 2;
+static int slow_work_max_max_threads = 255;
+static const int slow_work_min_vslow = 1;
+static const int slow_work_max_vslow = 99;
+
+ctl_table slow_work_sysctls[] = {
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "min-threads",
+ .data = &slow_work_min_threads,
+ .maxlen = sizeof(unsigned),
+ .mode = 0644,
+ .proc_handler = slow_work_min_threads_sysctl,
+ .extra1 = (void *) &slow_work_min_min_threads,
+ .extra2 = &slow_work_max_threads,
+ },
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "max-threads",
+ .data = &slow_work_max_threads,
+ .maxlen = sizeof(unsigned),
+ .mode = 0644,
+ .proc_handler = slow_work_max_threads_sysctl,
+ .extra1 = &slow_work_min_threads,
+ .extra2 = (void *) &slow_work_max_max_threads,
+ },
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "vslow-percentage",
+ .data = &vslow_work_proportion,
+ .maxlen = sizeof(unsigned),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .extra1 = (void *) &slow_work_min_vslow,
+ .extra2 = (void *) &slow_work_max_vslow,
+ },
+ { .ctl_name = 0 }
+};
+#endif
+
+/*
+ * The active state of the thread pool
+ */
static atomic_t slow_work_thread_count;
static atomic_t vslow_work_executing_count;
+static bool slow_work_may_not_start_new_thread;
+static bool slow_work_cull; /* cull a thread due to lack of activity */
+static DEFINE_TIMER(slow_work_cull_timer, slow_work_cull_timeout, 0, 0);
+static DEFINE_TIMER(slow_work_oom_timer, slow_work_oom_timeout, 0, 0);
+static struct slow_work slow_work_new_thread; /* new thread starter */
+
/*
* The queues of work items and the lock governing access to them. These are
* shared between all the CPUs. It doesn't make sense to have per-CPU queues
vsmax = slow_work_calc_vsmax();
+ /* see if we can schedule a new thread to be started if we're not
+ * keeping up with the work */
+ if (!waitqueue_active(&slow_work_thread_wq) &&
+ (!list_empty(&slow_work_queue) || !list_empty(&vslow_work_queue)) &&
+ atomic_read(&slow_work_thread_count) < slow_work_max_threads &&
+ !slow_work_may_not_start_new_thread)
+ slow_work_enqueue(&slow_work_new_thread);
+
/* find something to execute */
spin_lock_irq(&slow_work_queue_lock);
if (!list_empty(&vslow_work_queue) &&
}
EXPORT_SYMBOL(slow_work_enqueue);
+/*
+ * Worker thread culling algorithm
+ */
+static bool slow_work_cull_thread(void)
+{
+ unsigned long flags;
+ bool do_cull = false;
+
+ spin_lock_irqsave(&slow_work_queue_lock, flags);
+
+ if (slow_work_cull) {
+ slow_work_cull = false;
+
+ if (list_empty(&slow_work_queue) &&
+ list_empty(&vslow_work_queue) &&
+ atomic_read(&slow_work_thread_count) >
+ slow_work_min_threads) {
+ mod_timer(&slow_work_cull_timer,
+ jiffies + SLOW_WORK_CULL_TIMEOUT);
+ do_cull = true;
+ }
+ }
+
+ spin_unlock_irqrestore(&slow_work_queue_lock, flags);
+ return do_cull;
+}
+
/*
* Determine if there is slow work available for dispatch
*/
TASK_INTERRUPTIBLE);
if (!freezing(current) &&
!slow_work_threads_should_exit &&
- !slow_work_available(vsmax))
+ !slow_work_available(vsmax) &&
+ !slow_work_cull)
schedule();
finish_wait(&slow_work_thread_wq, &wait);
if (slow_work_available(vsmax) && slow_work_execute()) {
cond_resched();
+ if (list_empty(&slow_work_queue) &&
+ list_empty(&vslow_work_queue) &&
+ atomic_read(&slow_work_thread_count) >
+ slow_work_min_threads)
+ mod_timer(&slow_work_cull_timer,
+ jiffies + SLOW_WORK_CULL_TIMEOUT);
continue;
}
if (slow_work_threads_should_exit)
break;
+
+ if (slow_work_cull && slow_work_cull_thread())
+ break;
}
if (atomic_dec_and_test(&slow_work_thread_count))
return 0;
}
+/*
+ * Handle thread cull timer expiration
+ */
+static void slow_work_cull_timeout(unsigned long data)
+{
+ slow_work_cull = true;
+ wake_up(&slow_work_thread_wq);
+}
+
+/*
+ * Get a reference on slow work thread starter
+ */
+static int slow_work_new_thread_get_ref(struct slow_work *work)
+{
+ return 0;
+}
+
+/*
+ * Drop a reference on slow work thread starter
+ */
+static void slow_work_new_thread_put_ref(struct slow_work *work)
+{
+}
+
+/*
+ * Start a new slow work thread
+ */
+static void slow_work_new_thread_execute(struct slow_work *work)
+{
+ struct task_struct *p;
+
+ if (slow_work_threads_should_exit)
+ return;
+
+ if (atomic_read(&slow_work_thread_count) >= slow_work_max_threads)
+ return;
+
+ if (!mutex_trylock(&slow_work_user_lock))
+ return;
+
+ slow_work_may_not_start_new_thread = true;
+ atomic_inc(&slow_work_thread_count);
+ p = kthread_run(slow_work_thread, NULL, "kslowd");
+ if (IS_ERR(p)) {
+ printk(KERN_DEBUG "Slow work thread pool: OOM\n");
+ if (atomic_dec_and_test(&slow_work_thread_count))
+ BUG(); /* we're running on a slow work thread... */
+ mod_timer(&slow_work_oom_timer,
+ jiffies + SLOW_WORK_OOM_TIMEOUT);
+ } else {
+ /* ratelimit the starting of new threads */
+ mod_timer(&slow_work_oom_timer, jiffies + 1);
+ }
+
+ mutex_unlock(&slow_work_user_lock);
+}
+
+static const struct slow_work_ops slow_work_new_thread_ops = {
+ .get_ref = slow_work_new_thread_get_ref,
+ .put_ref = slow_work_new_thread_put_ref,
+ .execute = slow_work_new_thread_execute,
+};
+
+/*
+ * post-OOM new thread start suppression expiration
+ */
+static void slow_work_oom_timeout(unsigned long data)
+{
+ slow_work_may_not_start_new_thread = false;
+}
+
+#ifdef CONFIG_SYSCTL
+/*
+ * Handle adjustment of the minimum number of threads
+ */
+static int slow_work_min_threads_sysctl(struct ctl_table *table, int write,
+ struct file *filp, void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+ int n;
+
+ if (ret == 0) {
+ mutex_lock(&slow_work_user_lock);
+ if (slow_work_user_count > 0) {
+ /* see if we need to start or stop threads */
+ n = atomic_read(&slow_work_thread_count) -
+ slow_work_min_threads;
+
+ if (n < 0 && !slow_work_may_not_start_new_thread)
+ slow_work_enqueue(&slow_work_new_thread);
+ else if (n > 0)
+ mod_timer(&slow_work_cull_timer,
+ jiffies + SLOW_WORK_CULL_TIMEOUT);
+ }
+ mutex_unlock(&slow_work_user_lock);
+ }
+
+ return ret;
+}
+
+/*
+ * Handle adjustment of the maximum number of threads
+ */
+static int slow_work_max_threads_sysctl(struct ctl_table *table, int write,
+ struct file *filp, void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+ int n;
+
+ if (ret == 0) {
+ mutex_lock(&slow_work_user_lock);
+ if (slow_work_user_count > 0) {
+ /* see if we need to stop threads */
+ n = slow_work_max_threads -
+ atomic_read(&slow_work_thread_count);
+
+ if (n < 0)
+ mod_timer(&slow_work_cull_timer,
+ jiffies + SLOW_WORK_CULL_TIMEOUT);
+ }
+ mutex_unlock(&slow_work_user_lock);
+ }
+
+ return ret;
+}
+#endif /* CONFIG_SYSCTL */
+
/**
* slow_work_register_user - Register a user of the facility
*
init_completion(&slow_work_last_thread_exited);
slow_work_threads_should_exit = false;
+ slow_work_init(&slow_work_new_thread,
+ &slow_work_new_thread_ops);
+ slow_work_may_not_start_new_thread = false;
+ slow_work_cull = false;
/* start the minimum number of threads */
for (loop = 0; loop < slow_work_min_threads; loop++) {
" Shut down complete\n");
}
+ del_timer_sync(&slow_work_cull_timer);
+
mutex_unlock(&slow_work_user_lock);
}
EXPORT_SYMBOL(slow_work_unregister_user);
{
unsigned nr_cpus = num_possible_cpus();
- if (nr_cpus > slow_work_max_threads)
+ if (slow_work_max_threads < nr_cpus)
slow_work_max_threads = nr_cpus;
+#ifdef CONFIG_SYSCTL
+ if (slow_work_max_max_threads < nr_cpus * 2)
+ slow_work_max_max_threads = nr_cpus * 2;
+#endif
return 0;
}
projects / linux-2.6-omap-h63xx.git / blobdiff