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writeback: disable periodic old data writeback for !dirty_writeback_centisecs

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Prior to 2.6.32, setting /proc/sys/vm/dirty_writeback_centisecs disabled
periodic dirty writeback from kupdate. This got broken and now causes
excessive sys CPU usage if set to zero, as we'll keep beating on
schedule().

Cc: stable@kernel.org
Reported-by: Justin Maggard <jmaggard10@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2010-05-17 12:51:03 +02:00
parent 2395e463fe
commit 69b62d01ec
1 changed files with 12 additions and 2 deletions
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14
fs/fs-writeback.c
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@ -852,6 +852,12 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
unsigned long expired;
long nr_pages;
/*
* When set to zero, disable periodic writeback
*/
if (!dirty_writeback_interval)
return 0;
expired = wb->last_old_flush +
msecs_to_jiffies(dirty_writeback_interval * 10);
if (time_before(jiffies, expired))
@ -947,8 +953,12 @@ int bdi_writeback_task(struct bdi_writeback *wb)
break;
}
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
schedule_timeout_interruptible(wait_jiffies);
if (dirty_writeback_interval) {
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
schedule_timeout_interruptible(wait_jiffies);
} else
schedule();
try_to_freeze();
}