diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2013-03-01 22:45:49 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2013-03-01 22:45:49 +0000 |
| commit | df5d2e9089c7d5b8c46f767e4278610ea3e815b9 (patch) | |
| tree | 5285aa8b0c794da419133a209437b32a11aa8a8d /include | |
| parent | a26062416ef8add48f16fbadded2b5f6fb84d024 (diff) | |
dm kcopyd: introduce configurable throttling
This patch allows the administrator to reduce the rate at which kcopyd
issues I/O.
Each module that uses kcopyd acquires a throttle parameter that can be
set in /sys/module/*/parameters.
We maintain a history of kcopyd usage by each module in the variables
io_period and total_period in struct dm_kcopyd_throttle. The actual
kcopyd activity is calculated as a percentage of time equal to
"(100 * io_period / total_period)". This is compared with the user-defined
throttle percentage threshold and if it is exceeded, we sleep.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/dm-kcopyd.h | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/include/linux/dm-kcopyd.h b/include/linux/dm-kcopyd.h index 47d9d376e4e..f486d636b82 100644 --- a/include/linux/dm-kcopyd.h +++ b/include/linux/dm-kcopyd.h @@ -21,11 +21,34 @@ #define DM_KCOPYD_IGNORE_ERROR 1 +struct dm_kcopyd_throttle { + unsigned throttle; + unsigned num_io_jobs; + unsigned io_period; + unsigned total_period; + unsigned last_jiffies; +}; + +/* + * kcopyd clients that want to support throttling must pass an initialised + * dm_kcopyd_throttle struct into dm_kcopyd_client_create(). + * Two or more clients may share the same instance of this struct between + * them if they wish to be throttled as a group. + * + * This macro also creates a corresponding module parameter to configure + * the amount of throttling. + */ +#define DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(name, description) \ +static struct dm_kcopyd_throttle dm_kcopyd_throttle = { 100, 0, 0, 0, 0 }; \ +module_param_named(name, dm_kcopyd_throttle.throttle, uint, 0644); \ +MODULE_PARM_DESC(name, description) + /* * To use kcopyd you must first create a dm_kcopyd_client object. + * throttle can be NULL if you don't want any throttling. */ struct dm_kcopyd_client; -struct dm_kcopyd_client *dm_kcopyd_client_create(void); +struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle); void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc); /* |