diff options
Diffstat (limited to 'mm/pdflush.c')
| -rw-r--r-- | mm/pdflush.c | 49 |
1 files changed, 37 insertions, 12 deletions
diff --git a/mm/pdflush.c b/mm/pdflush.c index 15de509b68fd..f2caf96993f8 100644 --- a/mm/pdflush.c +++ b/mm/pdflush.c @@ -58,6 +58,14 @@ static DEFINE_SPINLOCK(pdflush_lock); int nr_pdflush_threads = 0; /* + * The max/min number of pdflush threads. R/W by sysctl at + * /proc/sys/vm/nr_pdflush_threads_max/min + */ +int nr_pdflush_threads_max __read_mostly = MAX_PDFLUSH_THREADS; +int nr_pdflush_threads_min __read_mostly = MIN_PDFLUSH_THREADS; + + +/* * The time at which the pdflush thread pool last went empty */ static unsigned long last_empty_jifs; @@ -68,7 +76,7 @@ static unsigned long last_empty_jifs; * Thread pool management algorithm: * * - The minimum and maximum number of pdflush instances are bound - * by MIN_PDFLUSH_THREADS and MAX_PDFLUSH_THREADS. + * by nr_pdflush_threads_min and nr_pdflush_threads_max. * * - If there have been no idle pdflush instances for 1 second, create * a new one. @@ -98,7 +106,6 @@ static int __pdflush(struct pdflush_work *my_work) INIT_LIST_HEAD(&my_work->list); spin_lock_irq(&pdflush_lock); - nr_pdflush_threads++; for ( ; ; ) { struct pdflush_work *pdf; @@ -126,20 +133,25 @@ static int __pdflush(struct pdflush_work *my_work) (*my_work->fn)(my_work->arg0); + spin_lock_irq(&pdflush_lock); + /* * Thread creation: For how long have there been zero * available threads? + * + * To throttle creation, we reset last_empty_jifs. */ if (time_after(jiffies, last_empty_jifs + 1 * HZ)) { - /* unlocked list_empty() test is OK here */ - if (list_empty(&pdflush_list)) { - /* unlocked test is OK here */ - if (nr_pdflush_threads < MAX_PDFLUSH_THREADS) - start_one_pdflush_thread(); + if (list_empty(&pdflush_list) && + nr_pdflush_threads < nr_pdflush_threads_max) { + last_empty_jifs = jiffies; + nr_pdflush_threads++; + spin_unlock_irq(&pdflush_lock); + start_one_pdflush_thread(); + spin_lock_irq(&pdflush_lock); } } - spin_lock_irq(&pdflush_lock); my_work->fn = NULL; /* @@ -148,7 +160,7 @@ static int __pdflush(struct pdflush_work *my_work) */ if (list_empty(&pdflush_list)) continue; - if (nr_pdflush_threads <= MIN_PDFLUSH_THREADS) + if (nr_pdflush_threads <= nr_pdflush_threads_min) continue; pdf = list_entry(pdflush_list.prev, struct pdflush_work, list); if (time_after(jiffies, pdf->when_i_went_to_sleep + 1 * HZ)) { @@ -191,7 +203,7 @@ static int pdflush(void *dummy) /* * Some configs put our parent kthread in a limited cpuset, - * which kthread() overrides, forcing cpus_allowed == CPU_MASK_ALL. + * which kthread() overrides, forcing cpus_allowed == cpu_all_mask. * Our needs are more modest - cut back to our cpusets cpus_allowed. * This is needed as pdflush's are dynamically created and destroyed. * The boottime pdflush's are easily placed w/o these 2 lines. @@ -236,14 +248,27 @@ int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0) static void start_one_pdflush_thread(void) { - kthread_run(pdflush, NULL, "pdflush"); + struct task_struct *k; + + k = kthread_run(pdflush, NULL, "pdflush"); + if (unlikely(IS_ERR(k))) { + spin_lock_irq(&pdflush_lock); + nr_pdflush_threads--; + spin_unlock_irq(&pdflush_lock); + } } static int __init pdflush_init(void) { int i; - for (i = 0; i < MIN_PDFLUSH_THREADS; i++) + /* + * Pre-set nr_pdflush_threads... If we fail to create, + * the count will be decremented. + */ + nr_pdflush_threads = nr_pdflush_threads_min; + + for (i = 0; i < nr_pdflush_threads_min; i++) start_one_pdflush_thread(); return 0; } |