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Date: Wed, 8 Apr 2009 14:00:11 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
akpm@...ux-foundation.org, jack@...e.cz,
Jens Axboe <jens.axboe@...cle.com>
Subject: [PATCH 08/13] writeback: allow sleepy exit of default writeback task
Since we do lazy create of default writeback tasks for a bdi, we can
allow sleepy exit if it has been completely idle for 5 minutes.
Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
---
fs/fs-writeback.c | 44 +++++++++++++++++++++++++++++++++++-------
include/linux/backing-dev.h | 5 ++++
include/linux/writeback.h | 2 +-
3 files changed, 42 insertions(+), 9 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index bcca7c1..7ed86a0 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -153,9 +153,9 @@ int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
* older_than_this takes precedence over nr_to_write. So we'll only write back
* all dirty pages if they are all attached to "old" mappings.
*/
-void wb_kupdated(struct bdi_writeback *wb)
+long wb_kupdated(struct bdi_writeback *wb)
{
- long nr_to_write;
+ long nr_to_write, wrote = 0;
struct writeback_control wbc = {
.bdi = wb->bdi,
.sync_mode = WB_SYNC_NONE,
@@ -175,13 +175,16 @@ void wb_kupdated(struct bdi_writeback *wb)
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
generic_sync_bdi_inodes(NULL, &wbc);
+ wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
if (wbc.nr_to_write > 0)
break; /* All the old data is written */
nr_to_write -= MAX_WRITEBACK_PAGES;
}
+
+ return wrote;
}
-void wb_writeback(struct bdi_writeback *wb)
+long wb_writeback(struct bdi_writeback *wb)
{
struct writeback_control wbc = {
.bdi = wb->bdi,
@@ -189,7 +192,7 @@ void wb_writeback(struct bdi_writeback *wb)
.older_than_this = NULL,
.range_cyclic = 1,
};
- long nr_pages = wb->nr_pages;
+ long nr_pages = wb->nr_pages, wrote = 0;
for (;;) {
unsigned long background_thresh, dirty_thresh;
@@ -205,6 +208,7 @@ void wb_writeback(struct bdi_writeback *wb)
wbc.pages_skipped = 0;
generic_sync_wb_inodes(wb, wb->sb, &wbc);
nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
/*
* If we ran out of stuff to write, bail unless more_io got set
*/
@@ -214,14 +218,18 @@ void wb_writeback(struct bdi_writeback *wb)
break;
}
}
+
+ return wrote;
}
/*
* This will be inlined in bdi_writeback_task() once we get rid of any
* dirty inodes on the default_backing_dev_info
*/
-void wb_do_writeback(struct bdi_writeback *wb)
+long wb_do_writeback(struct bdi_writeback *wb)
{
+ long nr_pages;
+
/*
* We get here in two cases:
*
@@ -237,11 +245,12 @@ void wb_do_writeback(struct bdi_writeback *wb)
*
*/
if (writeback_acquire(wb))
- wb_kupdated(wb);
+ nr_pages = wb_kupdated(wb);
else
- wb_writeback(wb);
+ nr_pages = wb_writeback(wb);
writeback_release(wb);
+ return nr_pages;
}
/*
@@ -250,6 +259,9 @@ void wb_do_writeback(struct bdi_writeback *wb)
*/
int bdi_writeback_task(struct bdi_writeback *wb)
{
+ unsigned long last_active = jiffies;
+ long pages_written;
+
while (!kthread_should_stop()) {
unsigned long wait_jiffies;
DEFINE_WAIT(wait);
@@ -259,9 +271,25 @@ int bdi_writeback_task(struct bdi_writeback *wb)
schedule_timeout(wait_jiffies);
try_to_freeze();
- wb_do_writeback(wb);
+ pages_written = wb_do_writeback(wb);
finish_wait(&wb->wait, &wait);
+
+ if (pages_written)
+ last_active = jiffies;
+ else {
+ unsigned long max_idle;
+
+ /*
+ * Longest period of inactivity that we tolerate. If we
+ * see dirty data again later, the task will get
+ * recreated automatically.
+ */
+ max_idle = max(5UL * 60 * HZ, wait_jiffies);
+ if (time_after(jiffies, max_idle + last_active) &&
+ wb_is_default_task(wb))
+ break;
+ }
}
return 0;
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index c596bf6..ce23ec7 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -112,6 +112,11 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+static inline int wb_is_default_task(struct bdi_writeback *wb)
+{
+ return wb == &wb->bdi->wb;
+}
+
static inline int bdi_wblist_needs_lock(struct backing_dev_info *bdi)
{
return test_bit(BDI_wblist_lock, &bdi->state);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 2e08bbd..ddb10dc 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -69,7 +69,7 @@ void writeback_inodes(struct writeback_control *wbc);
int inode_wait(void *);
void sync_inodes_sb(struct super_block *, int wait);
void sync_inodes(int wait);
-void wb_do_writeback(struct bdi_writeback *wb);
+long wb_do_writeback(struct bdi_writeback *wb);
/* writeback.h requires fs.h; it, too, is not included from here. */
static inline void wait_on_inode(struct inode *inode)
--
1.6.2.2.446.gfbdc0
--
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