diff options
Diffstat (limited to 'drivers/md/dm-path-selector.h')
| -rw-r--r-- | drivers/md/dm-path-selector.h | 45 |
1 files changed, 30 insertions, 15 deletions
diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h index c47bc0e20275..7b2270532e64 100644 --- a/drivers/md/dm-path-selector.h +++ b/drivers/md/dm-path-selector.h @@ -1,3 +1,4 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ /* * Copyright (C) 2003 Sistina Software. * Copyright (C) 2004 Red Hat, Inc. All rights reserved. @@ -26,62 +27,76 @@ struct path_selector { void *context; }; +/* + * If a path selector uses this flag, a high resolution timer is used + * (via ktime_get_ns) to account for IO start time in BIO-based mpath. + * This improves performance of some path selectors (i.e. HST), in + * exchange for slightly higher overhead when submitting the BIO. + * The extra cost is usually offset by improved path selection for + * some benchmarks. + * + * This has no effect for request-based mpath, since it already uses a + * higher precision timer by default. + */ +#define DM_PS_USE_HR_TIMER 0x00000001 +#define dm_ps_use_hr_timer(type) ((type)->features & DM_PS_USE_HR_TIMER) + /* Information about a path selector type */ struct path_selector_type { char *name; struct module *module; + unsigned int features; unsigned int table_args; unsigned int info_args; /* * Constructs a path selector object, takes custom arguments */ - int (*create) (struct path_selector *ps, unsigned argc, char **argv); - void (*destroy) (struct path_selector *ps); + int (*create)(struct path_selector *ps, unsigned int argc, char **argv); + void (*destroy)(struct path_selector *ps); /* * Add an opaque path object, along with some selector specific * path args (eg, path priority). */ - int (*add_path) (struct path_selector *ps, struct dm_path *path, - int argc, char **argv, char **error); + int (*add_path)(struct path_selector *ps, struct dm_path *path, + int argc, char **argv, char **error); /* * Chooses a path for this io, if no paths are available then * NULL will be returned. */ - struct dm_path *(*select_path) (struct path_selector *ps, - size_t nr_bytes); + struct dm_path *(*select_path)(struct path_selector *ps, size_t nr_bytes); /* * Notify the selector that a path has failed. */ - void (*fail_path) (struct path_selector *ps, struct dm_path *p); + void (*fail_path)(struct path_selector *ps, struct dm_path *p); /* * Ask selector to reinstate a path. */ - int (*reinstate_path) (struct path_selector *ps, struct dm_path *p); + int (*reinstate_path)(struct path_selector *ps, struct dm_path *p); /* * Table content based on parameters added in ps_add_path_fn * or path selector status */ - int (*status) (struct path_selector *ps, struct dm_path *path, - status_type_t type, char *result, unsigned int maxlen); + int (*status)(struct path_selector *ps, struct dm_path *path, + status_type_t type, char *result, unsigned int maxlen); - 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, u64 start_time); + 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, u64 start_time); }; /* Register a path selector */ int dm_register_path_selector(struct path_selector_type *type); /* Unregister a path selector */ -int dm_unregister_path_selector(struct path_selector_type *type); +void dm_unregister_path_selector(struct path_selector_type *type); /* Returns a registered path selector type */ struct path_selector_type *dm_get_path_selector(const char *name); |