mm: add /proc controls for pdflush threads

[linux-2.6-omap-h63xx.git] / mm / pdflush.c

diff --git a/mm/pdflush.c b/mm/pdflush.c
index 235ac440c44e186b916925de3bcaa6f085518963..f2caf96993f851050a90b88d449ff13084da1c58 100644 (file)
--- a/mm/pdflush.c
+++ b/mm/pdflush.c
@@ -57,6 +57,14 @@ 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
  */
@@ -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.
@@ -134,14 +142,13 @@ static int __pdflush(struct pdflush_work *my_work)
                 * To throttle creation, we reset last_empty_jifs.
                 */
                if (time_after(jiffies, last_empty_jifs + 1 * HZ)) {
-                       if (list_empty(&pdflush_list)) {
-                               if (nr_pdflush_threads < MAX_PDFLUSH_THREADS) {
-                                       last_empty_jifs = jiffies;
-                                       nr_pdflush_threads++;
-                                       spin_unlock_irq(&pdflush_lock);
-                                       start_one_pdflush_thread();
-                                       spin_lock_irq(&pdflush_lock);
-                               }
+                       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);
                        }
                }
 
@@ -153,7 +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)) {
@@ -259,9 +266,9 @@ static int __init pdflush_init(void)
         * Pre-set nr_pdflush_threads...  If we fail to create,
         * the count will be decremented.
         */
-       nr_pdflush_threads = MIN_PDFLUSH_THREADS;
+       nr_pdflush_threads = nr_pdflush_threads_min;
 
-       for (i = 0; i < MIN_PDFLUSH_THREADS; i++)
+       for (i = 0; i < nr_pdflush_threads_min; i++)
                start_one_pdflush_thread();
        return 0;
 }