GitHub-Mirror/linux-bl808
2
0
Fork 0
mirror of https://github.com/Fishwaldo/linux-bl808.git synced 2025-06-17 20:25:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

block: add sysfs knob for turning off disk entropy contributions

Browse source 
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>
This commit is contained in:
Jens Axboe 2010-06-09 10:42:09 +02:00
parent 841fdffdd3
commit e2e1a148bc
3 changed files with 34 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

5
include/linux/blkdev.h
View file

@ -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)