On Wed, Feb 10 2016 at 5:35am -0500,
Joe Thornber <ejt@xxxxxxxxxx> wrote:
> smq seems to be performing better than the old mq policy in all
> situations, as well as using a quarter of the memory.
>
> This patch makes 'mq' and alias for 'smq' when choosing a cache
> policy. The tunables that were present for the old mq are faked, and
> have no effect. mq should be considered deprecated now.
> ---
> drivers/md/Kconfig | 11 +-
> drivers/md/Makefile | 2 -
> drivers/md/dm-cache-policy-mq.c | 1472 --------------------------------------
> drivers/md/dm-cache-policy-smq.c | 93 ++-
> drivers/md/dm-cache-policy.c | 6 +-
> 5 files changed, 97 insertions(+), 1487 deletions(-)
> delete mode 100644 drivers/md/dm-cache-policy-mq.c
>
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index b871928..9ea570b 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -295,14 +295,11 @@ config DM_CACHE
> cleaned etc. It supports writeback and writethrough modes.
>
> config DM_CACHE_MQ
> - tristate "MQ Cache Policy (EXPERIMENTAL)"
> - depends on DM_CACHE
> - default y
> + tristate "MQ Cache Policy (DEPRECATED)"
> + depends on DM_CACHE_SMQ
> + default n
> ---help---
> - A cache policy that uses a multiqueue ordered by recent hit
> - count to select which blocks should be promoted and demoted.
> - This is meant to be a general purpose policy. It prioritises
> - reads over writes.
> + This policy is now an alias for the SMQ policy.
>
> config DM_CACHE_SMQ
> tristate "Stochastic MQ Cache Policy (EXPERIMENTAL)"
...
> diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
> deleted file mode 100644
> index dbdabdf..0000000
> --- a/drivers/md/dm-cache-policy-mq.c
> +++ /dev/null
<snip delete of dm-cache-policy-mq.c>
> diff --git a/drivers/md/dm-cache-policy-smq.c b/drivers/md/dm-cache-policy-smq.c
> index 1ffbeb1..8ad6b22 100644
> --- a/drivers/md/dm-cache-policy-smq.c
> +++ b/drivers/md/dm-cache-policy-smq.c
...
> @@ -1716,6 +1781,15 @@ static struct dm_cache_policy_type smq_policy_type = {
> .create = smq_create
> };
>
> +static struct dm_cache_policy_type mq_policy_type = {
> + .name = "mq",
> + .version = {1, 4, 0},
> + .hint_size = 4,
> + .owner = THIS_MODULE,
> + .create = mq_create,
> + .real = &mq_policy_type
> +};
> +
> static struct dm_cache_policy_type default_policy_type = {
> .name = "default",
> .version = {1, 4, 0},
> @@ -1735,9 +1809,17 @@ static int __init smq_init(void)
> return -ENOMEM;
> }
>
> + r = dm_cache_policy_register(&mq_policy_type);
> + if (r) {
> + DMERR("register failed %d", r);
> + dm_cache_policy_unregister(&smq_policy_type);
> + return -ENOMEM;
> + }
> +
> r = dm_cache_policy_register(&default_policy_type);
> if (r) {
> DMERR("register failed (as default) %d", r);
> + dm_cache_policy_unregister(&mq_policy_type);
> dm_cache_policy_unregister(&smq_policy_type);
> return -ENOMEM;
> }
> @@ -1748,6 +1830,7 @@ static int __init smq_init(void)
> static void __exit smq_exit(void)
> {
> dm_cache_policy_unregister(&smq_policy_type);
> + dm_cache_policy_unregister(&mq_policy_type);
> dm_cache_policy_unregister(&default_policy_type);
> }
>
> diff --git a/drivers/md/dm-cache-policy.c b/drivers/md/dm-cache-policy.c
> index c1a3cee..829f3af 100644
> --- a/drivers/md/dm-cache-policy.c
> +++ b/drivers/md/dm-cache-policy.c
> @@ -62,7 +62,11 @@ static struct dm_cache_policy_type *get_policy(const char *name)
> if (t)
> return t;
>
> - request_module("dm-cache-%s", name);
> + /* hack; mq is in the smq module */
> + if (!strcmp(name, "mq"))
> + request_module("dm-cache-smq");
> + else
> + request_module("dm-cache-%s", name);
>
> t = get_policy_once(name);
> if (IS_ERR(t))
> --
> 2.5.0
I don't think we need this get_policy() hack. We just want "mq" to be
an alias for "smq" no? Same as "default".
The new call to dm_cache_policy_register(&mq_policy_type) will add the
mq_policy_type to dm-cache-policy.c:register_list
Shouldn't get_policy()'s call to get_policy_once() resolve "mq" to be
"smq" if we just add this to the bottom of dm-cache-policy-smq?:
MODULE_ALIAS("dm-cache-mq");
I'm also missing why mq_policy_type's .real points to itself via
&mq_policy_type -- shouldn't it be &smq_policy_type (like "default"
does)?
Or is this some subtle compatability so that "mq" is always displayed
in cache status output?
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