diff options
| -rw-r--r-- | Documentation/md.txt | 6 | ||||
| -rw-r--r-- | drivers/md/raid5.c | 122 | ||||
| -rw-r--r-- | include/linux/raid/raid5.h | 7 |
3 files changed, 125 insertions, 10 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt index 396cdd9..a8b4306 100644 --- a/Documentation/md.txt +++ b/Documentation/md.txt @@ -450,3 +450,9 @@ These currently include there are upper and lower limits (32768, 16). Default is 128. strip_cache_active (currently raid5 only) number of active entries in the stripe cache + preread_bypass_threshold (currently raid5 only) + number of times a stripe requiring preread will be bypassed by + a stripe that does not require preread. For fairness defaults + to 1. Setting this to 0 disables bypass accounting and + requires preread stripes to wait until all full-width stripe- + writes are complete. Valid values are 0 to stripe_cache_size. diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 4efec46..45eead6 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -63,6 +63,7 @@ #define STRIPE_SHIFT (PAGE_SHIFT - 9) #define STRIPE_SECTORS (STRIPE_SIZE>>9) #define IO_THRESHOLD 1 +#define BYPASS_THRESHOLD 1 #define NR_HASH (PAGE_SIZE / sizeof(struct hlist_head)) #define HASH_MASK (NR_HASH - 1) @@ -398,6 +399,7 @@ static void ops_run_io(struct stripe_head *sh) might_sleep(); + set_bit(STRIPE_IO_STARTED, &sh->state); for (i = disks; i--; ) { int rw; struct bio *bi; @@ -1720,6 +1722,9 @@ handle_write_operations5(struct stripe_head *sh, int rcw, int expand) locked++; } } + if (locked + 1 == disks) + if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state)) + atomic_inc(&sh->raid_conf->pending_full_writes); } else { BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) || test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags))); @@ -1947,6 +1952,9 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh, STRIPE_SECTORS, 0, 0); } + if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state)) + if (atomic_dec_and_test(&conf->pending_full_writes)) + md_wakeup_thread(conf->mddev->thread); } /* __handle_issuing_new_read_requests5 - returns 0 if there are no more disks @@ -2149,6 +2157,10 @@ static void handle_completed_write_requests(raid5_conf_t *conf, 0); } } + + if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state)) + if (atomic_dec_and_test(&conf->pending_full_writes)) + md_wakeup_thread(conf->mddev->thread); } static void handle_issuing_new_write_requests5(raid5_conf_t *conf, @@ -2333,6 +2345,9 @@ static void handle_issuing_new_write_requests6(raid5_conf_t *conf, s->locked++; set_bit(R5_Wantwrite, &sh->dev[i].flags); } + if (s->locked == disks) + if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state)) + atomic_inc(&conf->pending_full_writes); /* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */ set_bit(STRIPE_INSYNC, &sh->state); @@ -3094,6 +3109,8 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page) else continue; + set_bit(STRIPE_IO_STARTED, &sh->state); + bi = &sh->dev[i].req; bi->bi_rw = rw; @@ -3164,7 +3181,7 @@ static void raid5_activate_delayed(raid5_conf_t *conf) clear_bit(STRIPE_DELAYED, &sh->state); if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) atomic_inc(&conf->preread_active_stripes); - list_add_tail(&sh->lru, &conf->handle_list); + list_add_tail(&sh->lru, &conf->hold_list); } } else blk_plug_device(conf->mddev->queue); @@ -3442,6 +3459,58 @@ static int chunk_aligned_read(struct request_queue *q, struct bio * raid_bio) } } +/* __get_priority_stripe - get the next stripe to process + * + * Full stripe writes are allowed to pass preread active stripes up until + * the bypass_threshold is exceeded. In general the bypass_count + * increments when the handle_list is handled before the hold_list; however, it + * will not be incremented when STRIPE_IO_STARTED is sampled set signifying a + * stripe with in flight i/o. The bypass_count will be reset when the + * head of the hold_list has changed, i.e. the head was promoted to the + * handle_list. + */ +static struct stripe_head *__get_priority_stripe(raid5_conf_t *conf) +{ + struct stripe_head *sh; + + pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n", + __func__, + list_empty(&conf->handle_list) ? "empty" : "busy", + list_empty(&conf->hold_list) ? "empty" : "busy", + atomic_read(&conf->pending_full_writes), conf->bypass_count); + + if (!list_empty(&conf->handle_list)) { + sh = list_entry(conf->handle_list.next, typeof(*sh), lru); + + if (list_empty(&conf->hold_list)) + conf->bypass_count = 0; + else if (!test_bit(STRIPE_IO_STARTED, &sh->state)) { + if (conf->hold_list.next == conf->last_hold) + conf->bypass_count++; + else { + conf->last_hold = conf->hold_list.next; + conf->bypass_count -= conf->bypass_threshold; + if (conf->bypass_count < 0) + conf->bypass_count = 0; + } + } + } else if (!list_empty(&conf->hold_list) && + ((conf->bypass_threshold && + conf->bypass_count > conf->bypass_threshold) || + atomic_read(&conf->pending_full_writes) == 0)) { + sh = list_entry(conf->hold_list.next, + typeof(*sh), lru); + conf->bypass_count -= conf->bypass_threshold; + if (conf->bypass_count < 0) + conf->bypass_count = 0; + } else + return NULL; + + list_del_init(&sh->lru); + atomic_inc(&sh->count); + BUG_ON(atomic_read(&sh->count) != 1); + return sh; +} static int make_request(struct request_queue *q, struct bio * bi) { @@ -3914,7 +3983,6 @@ static void raid5d(mddev_t *mddev) handled = 0; spin_lock_irq(&conf->device_lock); while (1) { - struct list_head *first; struct bio *bio; if (conf->seq_flush != conf->seq_write) { @@ -3936,17 +4004,12 @@ static void raid5d(mddev_t *mddev) handled++; } - if (list_empty(&conf->handle_list)) { + sh = __get_priority_stripe(conf); + + if (!sh) { async_tx_issue_pending_all(); break; } - - first = conf->handle_list.next; - sh = list_entry(first, struct stripe_head, lru); - - list_del_init(first); - atomic_inc(&sh->count); - BUG_ON(atomic_read(&sh->count)!= 1); spin_unlock_irq(&conf->device_lock); handled++; @@ -4011,6 +4074,42 @@ raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR, raid5_store_stripe_cache_size); static ssize_t +raid5_show_preread_threshold(mddev_t *mddev, char *page) +{ + raid5_conf_t *conf = mddev_to_conf(mddev); + if (conf) + return sprintf(page, "%d\n", conf->bypass_threshold); + else + return 0; +} + +static ssize_t +raid5_store_preread_threshold(mddev_t *mddev, const char *page, size_t len) +{ + raid5_conf_t *conf = mddev_to_conf(mddev); + char *end; + int new; + if (len >= PAGE_SIZE) + return -EINVAL; + if (!conf) + return -ENODEV; + + new = simple_strtoul(page, &end, 10); + if (!*page || (*end && *end != '\n')) + return -EINVAL; + if (new > conf->max_nr_stripes || new < 0) + return -EINVAL; + conf->bypass_threshold = new; + return len; +} + +static struct md_sysfs_entry +raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold, + S_IRUGO | S_IWUSR, + raid5_show_preread_threshold, + raid5_store_preread_threshold); + +static ssize_t stripe_cache_active_show(mddev_t *mddev, char *page) { raid5_conf_t *conf = mddev_to_conf(mddev); @@ -4026,6 +4125,7 @@ raid5_stripecache_active = __ATTR_RO(stripe_cache_active); static struct attribute *raid5_attrs[] = { &raid5_stripecache_size.attr, &raid5_stripecache_active.attr, + &raid5_preread_bypass_threshold.attr, NULL, }; static struct attribute_group raid5_attrs_group = { @@ -4130,12 +4230,14 @@ static int run(mddev_t *mddev) init_waitqueue_head(&conf->wait_for_stripe); init_waitqueue_head(&conf->wait_for_overlap); INIT_LIST_HEAD(&conf->handle_list); + INIT_LIST_HEAD(&conf->hold_list); INIT_LIST_HEAD(&conf->delayed_list); INIT_LIST_HEAD(&conf->bitmap_list); INIT_LIST_HEAD(&conf->inactive_list); atomic_set(&conf->active_stripes, 0); atomic_set(&conf->preread_active_stripes, 0); atomic_set(&conf->active_aligned_reads, 0); + conf->bypass_threshold = BYPASS_THRESHOLD; pr_debug("raid5: run(%s) called.\n", mdname(mddev)); diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h index 93678f5..f0827d3 100644 --- a/include/linux/raid/raid5.h +++ b/include/linux/raid/raid5.h @@ -252,6 +252,8 @@ struct r6_state { #define STRIPE_EXPANDING 9 #define STRIPE_EXPAND_SOURCE 10 #define STRIPE_EXPAND_READY 11 +#define STRIPE_IO_STARTED 12 /* do not count towards 'bypass_count' */ +#define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */ /* * Operations flags (in issue order) */ @@ -316,12 +318,17 @@ struct raid5_private_data { int previous_raid_disks; struct list_head handle_list; /* stripes needing handling */ + struct list_head hold_list; /* preread ready stripes */ struct list_head delayed_list; /* stripes that have plugged requests */ struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */ struct bio *retry_read_aligned; /* currently retrying aligned bios */ struct bio *retry_read_aligned_list; /* aligned bios retry list */ atomic_t preread_active_stripes; /* stripes with scheduled io */ atomic_t active_aligned_reads; + atomic_t pending_full_writes; /* full write backlog */ + int bypass_count; /* bypassed prereads */ + int bypass_threshold; /* preread nice */ + struct list_head *last_hold; /* detect hold_list promotions */ atomic_t reshape_stripes; /* stripes with pending writes for reshape */ /* unfortunately we need two cache names as we temporarily have |
