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authorMike Snitzer <snitzer@redhat.com>2015-06-17 11:43:38 -0400
committerMike Snitzer <snitzer@redhat.com>2015-06-17 12:40:38 -0400
commitbccab6a01afc26f53d91762d78153513cad10b29 (patch)
treea93caf5032b84668099e2ab35b7593cada04113c /drivers/md
parent6096d91af0b65a3967139b32d5adbb3647858a26 (diff)
dm cache: switch the "default" cache replacement policy from mq to smq
The Stochastic multiqueue (SMQ) policy (vs MQ) offers the promise of less memory utilization, improved performance and increased adaptability in the face of changing workloads. SMQ also does not have any cumbersome tuning knobs. Users may switch from "mq" to "smq" simply by appropriately reloading a DM table that is using the cache target. Doing so will cause all of the mq policy's hints to be dropped. Also, performance of the cache may degrade slightly until smq recalculates the origin device's hotspots that should be cached. In the future the "mq" policy will just silently make use of "smq" and the mq code will be removed. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-cache-policy-mq.c34
-rw-r--r--drivers/md/dm-cache-policy-smq.c17
2 files changed, 22 insertions, 29 deletions
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index 838665bb495a..32814371b8d3 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -1431,21 +1431,12 @@ bad_pre_cache_init:
static struct dm_cache_policy_type mq_policy_type = {
.name = "mq",
- .version = {1, 3, 0},
+ .version = {1, 4, 0},
.hint_size = 4,
.owner = THIS_MODULE,
.create = mq_create
};
-static struct dm_cache_policy_type default_policy_type = {
- .name = "default",
- .version = {1, 3, 0},
- .hint_size = 4,
- .owner = THIS_MODULE,
- .create = mq_create,
- .real = &mq_policy_type
-};
-
static int __init mq_init(void)
{
int r;
@@ -1455,36 +1446,21 @@ static int __init mq_init(void)
__alignof__(struct entry),
0, NULL);
if (!mq_entry_cache)
- goto bad;
+ return -ENOMEM;
r = dm_cache_policy_register(&mq_policy_type);
if (r) {
DMERR("register failed %d", r);
- goto bad_register_mq;
- }
-
- r = dm_cache_policy_register(&default_policy_type);
- if (!r) {
- DMINFO("version %u.%u.%u loaded",
- mq_policy_type.version[0],
- mq_policy_type.version[1],
- mq_policy_type.version[2]);
- return 0;
+ kmem_cache_destroy(mq_entry_cache);
+ return -ENOMEM;
}
- DMERR("register failed (as default) %d", r);
-
- dm_cache_policy_unregister(&mq_policy_type);
-bad_register_mq:
- kmem_cache_destroy(mq_entry_cache);
-bad:
- return -ENOMEM;
+ return 0;
}
static void __exit mq_exit(void)
{
dm_cache_policy_unregister(&mq_policy_type);
- dm_cache_policy_unregister(&default_policy_type);
kmem_cache_destroy(mq_entry_cache);
}
diff --git a/drivers/md/dm-cache-policy-smq.c b/drivers/md/dm-cache-policy-smq.c
index 66feb307e697..80f02d3330e2 100644
--- a/drivers/md/dm-cache-policy-smq.c
+++ b/drivers/md/dm-cache-policy-smq.c
@@ -1748,6 +1748,15 @@ static struct dm_cache_policy_type smq_policy_type = {
.create = smq_create
};
+static struct dm_cache_policy_type default_policy_type = {
+ .name = "default",
+ .version = {1, 0, 0},
+ .hint_size = 4,
+ .owner = THIS_MODULE,
+ .create = smq_create,
+ .real = &smq_policy_type
+};
+
static int __init smq_init(void)
{
int r;
@@ -1758,12 +1767,20 @@ static int __init smq_init(void)
return -ENOMEM;
}
+ r = dm_cache_policy_register(&default_policy_type);
+ if (r) {
+ DMERR("register failed (as default) %d", r);
+ dm_cache_policy_unregister(&smq_policy_type);
+ return -ENOMEM;
+ }
+
return 0;
}
static void __exit smq_exit(void)
{
dm_cache_policy_unregister(&smq_policy_type);
+ dm_cache_policy_unregister(&default_policy_type);
}
module_init(smq_init);