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-rw-r--r--Documentation/sysctl/vm.txt28
-rw-r--r--include/linux/writeback.h2
-rw-r--r--kernel/sysctl.c23
-rw-r--r--mm/pdflush.c31
4 files changed, 72 insertions, 12 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 3197fc8..97c4b32 100644
--- a/Documentation/sysctl/vm.txt
+++ b/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.
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 9344547..9c1ed1f 100644
--- a/include/linux/writeback.h
+++ b/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 */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b125e33..72eb1a4 100644
--- a/kernel/sysctl.c
+++ b/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;
@@ -1027,6 +1028,28 @@ static struct ctl_table vm_table[] = {
.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",
.data = &vm_swappiness,
diff --git a/mm/pdflush.c b/mm/pdflush.c
index 235ac44..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.
@@ -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;
}
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