diff options
| -rw-r--r-- | kernel/slow-work.c | 138 |
1 files changed, 137 insertions, 1 deletions
diff --git a/kernel/slow-work.c b/kernel/slow-work.c index 5a73927..454abb2 100644 --- a/kernel/slow-work.c +++ b/kernel/slow-work.c @@ -16,6 +16,14 @@ #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); + /* * The pool of threads has at least min threads in it as long as someone is * using the facility, and may have as many as max. @@ -29,6 +37,12 @@ static unsigned vslow_work_proportion = 50; /* % of threads that may process 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 @@ -89,6 +103,14 @@ static bool slow_work_execute(void) 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) && @@ -243,6 +265,33 @@ cant_get_ref: 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 */ static inline bool slow_work_available(int vsmax) @@ -273,7 +322,8 @@ static int slow_work_thread(void *_data) 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); @@ -285,11 +335,20 @@ static int slow_work_thread(void *_data) 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)) @@ -297,6 +356,77 @@ static int slow_work_thread(void *_data) 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; +} + /** * slow_work_register_user - Register a user of the facility * @@ -316,6 +446,10 @@ int slow_work_register_user(void) 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++) { @@ -369,6 +503,8 @@ void slow_work_unregister_user(void) " Shut down complete\n"); } + del_timer_sync(&slow_work_cull_timer); + mutex_unlock(&slow_work_user_lock); } EXPORT_SYMBOL(slow_work_unregister_user); |