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authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2010-07-25 15:29:22 +0400
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 20:53:56 +0400
commit6467716a37673e8d47b4984eb19839bdad0a8353 (patch)
tree8b2bfd38d53e31c47654162d4ce9220c4424a31d /include/linux/backing-dev.h
parent253c34e9b10c30d3064be654b5b78fbc1a8b1896 (diff)
downloadlinux-6467716a37673e8d47b4984eb19839bdad0a8353.tar.xz
writeback: optimize periodic bdi thread wakeups
Whe the first inode for a bdi is marked dirty, we wake up the bdi thread which should take care of the periodic background write-out. However, the write-out will actually start only 'dirty_writeback_interval' centisecs later, so we can delay the wake-up. This change was requested by Nick Piggin who pointed out that if we delay the wake-up, we weed out 2 unnecessary contex switches, which matters because '__mark_inode_dirty()' is a hot-path function. This patch introduces a new function - 'bdi_wakeup_thread_delayed()', which sets up a timer to wake-up the bdi thread and returns. So the wake-up is delayed. We also delete the timer in bdi threads just before writing-back. And synchronously delete it when unregistering bdi. At the unregister point the bdi does not have any users, so no one can arm it again. Since now we take 'bdi->wb_lock' in the timer, which can execute in softirq context, we have to use 'spin_lock_bh()' for 'bdi->wb_lock'. This patch makes this change as well. This patch also moves the 'bdi_wb_init()' function down in the file to avoid forward-declaration of 'bdi_wakeup_thread_delayed()'. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'include/linux/backing-dev.h')
-rw-r--r--include/linux/backing-dev.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 71b6223e0a77..7628219e5386 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -52,6 +52,7 @@ struct bdi_writeback {
unsigned long last_active; /* last time bdi thread was active */
struct task_struct *task; /* writeback thread */
+ struct timer_list wakeup_timer; /* used for delayed bdi thread wakeup */
struct list_head b_dirty; /* dirty inodes */
struct list_head b_io; /* parked for writeback */
struct list_head b_more_io; /* parked for more writeback */
@@ -105,6 +106,7 @@ void bdi_start_background_writeback(struct backing_dev_info *bdi);
int bdi_writeback_thread(void *data);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
void bdi_arm_supers_timer(void);
+void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;