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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 /block/blk-sysfs.c
parent841fdffdd382722d33579a6aa1487e8a4e526dbd (diff)
downloadlinux-stericsson-e2e1a148bc45855816ae6b4692ce29d0020fa22e.tar.gz
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 'block/blk-sysfs.c')
-rw-r--r--block/blk-sysfs.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 306759bbdf1b..58b53c354c2c 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,
};