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6467716a37
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> |
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