---

yaml
---
r: 142542
b: refs/heads/master
c: fafd688
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a56ed663047fc9927ec8b35750d23ece54f85dc7
+refs/heads/master: fafd688e4c0c34da0f3de909881117d374e4c7af

trunk/Documentation/sysctl/vm.txt

@@ -39,6 +39,8 @@ Currently, these files are in /proc/sys/vm:
 - nr_hugepages
 - nr_overcommit_hugepages
 - nr_pdflush_threads
+- nr_pdflush_threads_min
+- nr_pdflush_threads_max
 - nr_trim_pages         (only if CONFIG_MMU=n)
 - numa_zonelist_order
 - oom_dump_tasks
@@ -463,6 +465,32 @@ The default value is 0.
 
 ==============================================================
 
+nr_pdflush_threads_min
+
+This value controls the minimum number of pdflush threads.
+
+At boot time, the kernel will create and maintain 'nr_pdflush_threads_min'
+threads for the kernel's lifetime.
+
+The default value is 2.  The minimum value you can specify is 1, and
+the maximum value is the current setting of 'nr_pdflush_threads_max'.
+
+See 'nr_pdflush_threads_max' below for more information.
+
+==============================================================
+
+nr_pdflush_threads_max
+
+This value controls the maximum number of pdflush threads that can be
+created.  The pdflush algorithm will create a new pdflush thread (up to
+this maximum) if no pdflush threads have been available for >= 1 second.
+
+The default value is 8.  The minimum value you can specify is the
+current value of 'nr_pdflush_threads_min' and the
+maximum is 1000.
+
+==============================================================
+
 overcommit_memory:
 
 This value contains a flag that enables memory overcommitment.

trunk/include/linux/writeback.h

@@ -168,6 +168,8 @@ void writeback_set_ratelimit(void);
 /* pdflush.c */
 extern int nr_pdflush_threads;	/* Global so it can be exported to sysctl
 				   read-only. */
+extern int nr_pdflush_threads_max; /* Global so it can be exported to sysctl */
+extern int nr_pdflush_threads_min; /* Global so it can be exported to sysctl */
 
 
 #endif		/* WRITEBACK_H */

trunk/kernel/sysctl.c

@@ -101,6 +101,7 @@ static int __maybe_unused one = 1;
 static int __maybe_unused two = 2;
 static unsigned long one_ul = 1;
 static int one_hundred = 100;
+static int one_thousand = 1000;
 
 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
 static int maxolduid = 65535;
@@ -1026,6 +1027,28 @@ static struct ctl_table vm_table[] = {
 		.mode		= 0444 /* read-only*/,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "nr_pdflush_threads_min",
+		.data		= &nr_pdflush_threads_min,
+		.maxlen		= sizeof nr_pdflush_threads_min,
+		.mode		= 0644 /* read-write */,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &one,
+		.extra2		= &nr_pdflush_threads_max,
+	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "nr_pdflush_threads_max",
+		.data		= &nr_pdflush_threads_max,
+		.maxlen		= sizeof nr_pdflush_threads_max,
+		.mode		= 0644 /* read-write */,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &nr_pdflush_threads_min,
+		.extra2		= &one_thousand,
+	},
 	{
 		.ctl_name	= VM_SWAPPINESS,
 		.procname	= "swappiness",

trunk/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;
 }