diff options
| -rw-r--r-- | Documentation/ABI/testing/sysfs-block-dm | 14 | ||||
| -rw-r--r-- | drivers/md/dm-sysfs.c | 2 | ||||
| -rw-r--r-- | drivers/md/dm.c | 57 | ||||
| -rw-r--r-- | drivers/md/dm.h | 4 |
4 files changed, 73 insertions, 4 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-dm b/Documentation/ABI/testing/sysfs-block-dm index 87ca5691e29b..ac4b6fe245d9 100644 --- a/Documentation/ABI/testing/sysfs-block-dm +++ b/Documentation/ABI/testing/sysfs-block-dm @@ -23,3 +23,17 @@ Description: Device-mapper device suspend state. Contains the value 1 while the device is suspended. Otherwise it contains 0. Read-only attribute. Users: util-linux, device-mapper udev rules + +What: /sys/block/dm-<num>/dm/rq_based_seq_io_merge_deadline +Date: March 2015 +KernelVersion: 4.1 +Contact: dm-devel@redhat.com +Description: Allow control over how long a request that is a + reasonable merge candidate can be queued on the request + queue. The resolution of this deadline is in + microseconds (ranging from 1 to 100000 usecs). + Setting this attribute to 0 (the default) will disable + request-based DM's merge heuristic and associated extra + accounting. This attribute is not applicable to + bio-based DM devices so it will only ever report 0 for + them. diff --git a/drivers/md/dm-sysfs.c b/drivers/md/dm-sysfs.c index 1271c31709fd..f5bb3944f75e 100644 --- a/drivers/md/dm-sysfs.c +++ b/drivers/md/dm-sysfs.c @@ -92,11 +92,13 @@ static ssize_t dm_attr_suspended_show(struct mapped_device *md, char *buf) static DM_ATTR_RO(name); static DM_ATTR_RO(uuid); static DM_ATTR_RO(suspended); +static DM_ATTR_RW(rq_based_seq_io_merge_deadline); static struct attribute *dm_attrs[] = { &dm_attr_name.attr, &dm_attr_uuid.attr, &dm_attr_suspended.attr, + &dm_attr_rq_based_seq_io_merge_deadline.attr, NULL, }; diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 2ae78b31e4c0..5294e016e92b 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -21,6 +21,7 @@ #include <linux/delay.h> #include <linux/wait.h> #include <linux/kthread.h> +#include <linux/ktime.h> #include <linux/elevator.h> /* for rq_end_sector() */ #include <trace/events/block.h> @@ -219,8 +220,10 @@ struct mapped_device { struct task_struct *kworker_task; /* for request-based merge heuristic in dm_request_fn() */ - sector_t last_rq_pos; + unsigned seq_rq_merge_deadline_usecs; int last_rq_rw; + sector_t last_rq_pos; + ktime_t last_rq_start_time; }; /* @@ -1935,8 +1938,11 @@ static void dm_start_request(struct mapped_device *md, struct request *orig) blk_start_request(orig); atomic_inc(&md->pending[rq_data_dir(orig)]); - md->last_rq_pos = rq_end_sector(orig); - md->last_rq_rw = rq_data_dir(orig); + if (md->seq_rq_merge_deadline_usecs) { + md->last_rq_pos = rq_end_sector(orig); + md->last_rq_rw = rq_data_dir(orig); + md->last_rq_start_time = ktime_get(); + } /* * Hold the md reference here for the in-flight I/O. @@ -1948,6 +1954,45 @@ static void dm_start_request(struct mapped_device *md, struct request *orig) dm_get(md); } +#define MAX_SEQ_RQ_MERGE_DEADLINE_USECS 100000 + +ssize_t dm_attr_rq_based_seq_io_merge_deadline_show(struct mapped_device *md, char *buf) +{ + return sprintf(buf, "%u\n", md->seq_rq_merge_deadline_usecs); +} + +ssize_t dm_attr_rq_based_seq_io_merge_deadline_store(struct mapped_device *md, + const char *buf, size_t count) +{ + unsigned deadline; + + if (!dm_request_based(md)) + return count; + + if (kstrtouint(buf, 10, &deadline)) + return -EINVAL; + + if (deadline > MAX_SEQ_RQ_MERGE_DEADLINE_USECS) + deadline = MAX_SEQ_RQ_MERGE_DEADLINE_USECS; + + md->seq_rq_merge_deadline_usecs = deadline; + + return count; +} + +static bool dm_request_peeked_before_merge_deadline(struct mapped_device *md) +{ + ktime_t kt_deadline; + + if (!md->seq_rq_merge_deadline_usecs) + return false; + + kt_deadline = ns_to_ktime((u64)md->seq_rq_merge_deadline_usecs * NSEC_PER_USEC); + kt_deadline = ktime_add_safe(md->last_rq_start_time, kt_deadline); + + return !ktime_after(ktime_get(), kt_deadline); +} + /* * q->request_fn for request-based dm. * Called with the queue lock held. @@ -1990,7 +2035,8 @@ static void dm_request_fn(struct request_queue *q) continue; } - if (md_in_flight(md) && rq->bio && rq->bio->bi_vcnt == 1 && + if (dm_request_peeked_before_merge_deadline(md) && + md_in_flight(md) && rq->bio && rq->bio->bi_vcnt == 1 && md->last_rq_pos == pos && md->last_rq_rw == rq_data_dir(rq)) goto delay_and_out; @@ -2532,6 +2578,9 @@ static int dm_init_request_based_queue(struct mapped_device *md) if (!q) return 0; + /* disable dm_request_fn's merge heuristic by default */ + md->seq_rq_merge_deadline_usecs = 0; + md->queue = q; dm_init_md_queue(md); blk_queue_softirq_done(md->queue, dm_softirq_done); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index db495863fa5f..5522422cc6c4 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -234,4 +234,8 @@ static inline bool dm_message_test_buffer_overflow(char *result, unsigned maxlen return !maxlen || strlen(result) + 1 >= maxlen; } +ssize_t dm_attr_rq_based_seq_io_merge_deadline_show(struct mapped_device *md, char *buf); +ssize_t dm_attr_rq_based_seq_io_merge_deadline_store(struct mapped_device *md, + const char *buf, size_t count); + #endif |