diff options
| -rw-r--r-- | drivers/md/dm-mpath.c | 8 | ||||
| -rw-r--r-- | drivers/md/dm-path-selector.h | 15 | ||||
| -rw-r--r-- | drivers/md/dm-ps-historical-service-time.c | 1 |
3 files changed, 23 insertions, 1 deletions
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 6ed9d2731254..0e325469a252 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -105,6 +105,7 @@ struct multipath { struct dm_mpath_io { struct pgpath *pgpath; size_t nr_bytes; + u64 start_time_ns; }; typedef int (*action_fn) (struct pgpath *pgpath); @@ -295,6 +296,7 @@ static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mp mpio->nr_bytes = bio->bi_iter.bi_size; mpio->pgpath = NULL; + mpio->start_time_ns = 0; *mpio_p = mpio; dm_bio_record(bio_details, bio); @@ -647,6 +649,9 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, mpio->pgpath = pgpath; + if (dm_ps_use_hr_timer(pgpath->pg->ps.type)) + mpio->start_time_ns = ktime_get_ns(); + bio->bi_status = 0; bio_set_dev(bio, pgpath->path.dev->bdev); bio->bi_opf |= REQ_FAILFAST_TRANSPORT; @@ -1713,7 +1718,8 @@ done: if (ps->type->end_io) ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes, - dm_start_time_ns_from_clone(clone)); + (mpio->start_time_ns ?: + dm_start_time_ns_from_clone(clone))); } return r; diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h index c47bc0e20275..83cac2b04b66 100644 --- a/drivers/md/dm-path-selector.h +++ b/drivers/md/dm-path-selector.h @@ -26,11 +26,26 @@ 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; diff --git a/drivers/md/dm-ps-historical-service-time.c b/drivers/md/dm-ps-historical-service-time.c index 82f2a06153dc..1d82c95d323d 100644 --- a/drivers/md/dm-ps-historical-service-time.c +++ b/drivers/md/dm-ps-historical-service-time.c @@ -523,6 +523,7 @@ static int hst_end_io(struct path_selector *ps, struct dm_path *path, static struct path_selector_type hst_ps = { .name = "historical-service-time", .module = THIS_MODULE, + .features = DM_PS_USE_HR_TIMER, .table_args = 1, .info_args = 3, .create = hst_create, |