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-rw-r--r--mm/pdflush.c47
1 files changed, 36 insertions, 11 deletions
diff --git a/mm/pdflush.c b/mm/pdflush.c
index 118905e..f2caf96 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)) {
@@ -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;
}
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