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| author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2009-06-22 10:12:27 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2009-06-22 10:12:27 +0100 |
| commit | 02ab823fd1a27d193bda06b74fdad685a20a3e5e (patch) | |
| tree | 04b3db6e494f483fef34a55e487e88f6d7c585a5 /drivers/md/dm-path-selector.h | |
| parent | 2bd023452592e5f5cf90dd426cc39b7632b15b76 (diff) | |
| download | lwn-02ab823fd1a27d193bda06b74fdad685a20a3e5e.tar.gz lwn-02ab823fd1a27d193bda06b74fdad685a20a3e5e.zip | |
dm mpath: add start_io and nr_bytes to path selectors
This patch makes two additions to the dm path selector interface for
dynamic load balancers:
o a new hook, start_io()
o a new parameter 'nr_bytes' to select_path()/start_io()/end_io()
to pass the size of the I/O
start_io() is called when a target driver actually submits I/O
to the selected path.
Path selectors can use it to start accounting of the I/O.
(e.g. counting the number of in-flight I/Os.)
The start_io hook is based on the patch posted by Stefan Bader:
https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html
nr_bytes, the size of the I/O, is so path selectors can take the
size of the I/O into account when deciding which path to use.
dm-service-time uses it to estimate service time, for example.
(Added the nr_bytes member to dm_mpath_io instead of using existing
details.bi_size, since request-based dm patch deletes it.)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-path-selector.h')
| -rw-r--r-- | drivers/md/dm-path-selector.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h index 27357b85d73d..e7d1fa8b0459 100644 --- a/drivers/md/dm-path-selector.h +++ b/drivers/md/dm-path-selector.h @@ -56,7 +56,8 @@ struct path_selector_type { * the path fails. */ struct dm_path *(*select_path) (struct path_selector *ps, - unsigned *repeat_count); + unsigned *repeat_count, + size_t nr_bytes); /* * Notify the selector that a path has failed. @@ -75,7 +76,10 @@ struct path_selector_type { int (*status) (struct path_selector *ps, struct dm_path *path, status_type_t type, char *result, unsigned int maxlen); - int (*end_io) (struct path_selector *ps, struct dm_path *path); + int (*start_io) (struct path_selector *ps, struct dm_path *path, + size_t nr_bytes); + int (*end_io) (struct path_selector *ps, struct dm_path *path, + size_t nr_bytes); }; /* Register a path selector */ |