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| author | Jens Axboe <jaxboe@fusionio.com> | 2010-06-09 10:42:09 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2010-08-07 18:13:00 +0200 |
| commit | e2e1a148bc45855816ae6b4692ce29d0020fa22e (patch) | |
| tree | fd5ec8a580d4333b471acfe50f6f92b4cc880087 /include | |
| parent | cciss: new controller support and bump driver version (diff) | |
| download | linux-e2e1a148bc45855816ae6b4692ce29d0020fa22e.tar.xz linux-e2e1a148bc45855816ae6b4692ce29d0020fa22e.zip | |
block: add sysfs knob for turning off disk entropy contributions
There are two reasons for doing this:
- On SSD disks, the completion times aren't as random as they
are for rotational drives. So it's questionable whether they
should contribute to the random pool in the first place.
- Calling add_disk_randomness() has a lot of overhead.
This adds /sys/block/<dev>/queue/add_random that will allow you to
switch off on a per-device basis. The default setting is on, so there
should be no functional changes from this patch.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/blkdev.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 09a840264d6f..b8224ea4a5de 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -467,11 +467,13 @@ struct request_queue #define QUEUE_FLAG_IO_STAT 15 /* do IO stats */ #define QUEUE_FLAG_DISCARD 16 /* supports DISCARD */ #define QUEUE_FLAG_NOXMERGES 17 /* No extended merges */ +#define QUEUE_FLAG_ADD_RANDOM 18 /* Contributes to random pool */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_CLUSTER) | \ (1 << QUEUE_FLAG_STACKABLE) | \ - (1 << QUEUE_FLAG_SAME_COMP)) + (1 << QUEUE_FLAG_SAME_COMP) | \ + (1 << QUEUE_FLAG_ADD_RANDOM)) static inline int queue_is_locked(struct request_queue *q) { @@ -596,6 +598,7 @@ enum { test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags) #define blk_queue_nonrot(q) test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags) #define blk_queue_io_stat(q) test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags) +#define blk_queue_add_random(q) test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags) #define blk_queue_flushing(q) ((q)->ordseq) #define blk_queue_stackable(q) \ test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags) |