aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorJens Axboe <jaxboe@fusionio.com>2010-06-09 10:42:09 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 18:13:00 +0200
commite2e1a148bc45855816ae6b4692ce29d0020fa22e (patch)
treefd5ec8a580d4333b471acfe50f6f92b4cc880087
parent841fdffdd382722d33579a6aa1487e8a4e526dbd (diff)
downloadmrst-s0i3-test-e2e1a148bc45855816ae6b4692ce29d0020fa22e.tar.gz
mrst-s0i3-test-e2e1a148bc45855816ae6b4692ce29d0020fa22e.tar.xz
mrst-s0i3-test-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>
-rw-r--r--block/blk-core.c3
-rw-r--r--block/blk-sysfs.c28
-rw-r--r--include/linux/blkdev.h5
3 files changed, 34 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index f0640d7f800..b4131d29148 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2111,7 +2111,8 @@ static bool blk_update_bidi_request(struct request *rq, int error,
blk_update_request(rq->next_rq, error, bidi_bytes))
return true;
- add_disk_randomness(rq->rq_disk);
+ if (blk_queue_add_random(rq->q))
+ add_disk_randomness(rq->rq_disk);
return false;
}
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 306759bbdf1..58b53c354c2 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -250,6 +250,27 @@ queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
return ret;
}
+static ssize_t queue_random_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(blk_queue_add_random(q), page);
+}
+
+static ssize_t queue_random_store(struct request_queue *q, const char *page,
+ size_t count)
+{
+ unsigned long val;
+ ssize_t ret = queue_var_store(&val, page, count);
+
+ spin_lock_irq(q->queue_lock);
+ if (val)
+ queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q);
+ else
+ queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
+ spin_unlock_irq(q->queue_lock);
+
+ return ret;
+}
+
static ssize_t queue_iostats_show(struct request_queue *q, char *page)
{
return queue_var_show(blk_queue_io_stat(q), page);
@@ -374,6 +395,12 @@ static struct queue_sysfs_entry queue_iostats_entry = {
.store = queue_iostats_store,
};
+static struct queue_sysfs_entry queue_random_entry = {
+ .attr = {.name = "add_random", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_random_show,
+ .store = queue_random_store,
+};
+
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
@@ -394,6 +421,7 @@ static struct attribute *default_attrs[] = {
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
&queue_iostats_entry.attr,
+ &queue_random_entry.attr,
NULL,
};
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 09a840264d6..b8224ea4a5d 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)