On Thu, 5 Sep 2013 13:40:35 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> On Wed, Sep 04, 2013 at 04:41:32PM +1000, NeilBrown wrote:
> > On Tue, 3 Sep 2013 15:02:28 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> >
> > > On Tue, Sep 03, 2013 at 04:08:58PM +1000, NeilBrown wrote:
> > > > On Wed, 28 Aug 2013 14:39:53 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> > > >
> > > > > On Wed, Aug 28, 2013 at 02:32:52PM +1000, NeilBrown wrote:
> > > > > > On Tue, 27 Aug 2013 16:53:30 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> > > > > >
> > > > > > > On Tue, Aug 27, 2013 at 01:17:52PM +1000, NeilBrown wrote:
> > > > > >
> > > > > > >
> > > > > > > > Then get_active_stripe wouldn't need to worry about device_lock at all and
> > > > > > > > would only need to get the hash lock for the particular sector. That should
> > > > > > > > make it a lot simpler.
> > > > > > >
> > > > > > > did you mean get_active_stripe() doesn't need device_lock for any code path?
> > > > > > > How could it be safe? device_lock still protects something like handle_list,
> > > > > > > delayed_list, which release_stripe() will use while a get_active_stripe can run
> > > > > > > concurrently.
> > > > > >
> > > > > > Yes you will still need device_lock to protect list_del_init(&sh->lru),
> > > > > > as well as the hash lock.
> > > > > > Do you need device_lock anywhere else in there?
> > > > >
> > > > > That's what I mean. So I need get both device_lock and hash_lock. To not
> > > > > deadlock, I need release hash_lock and relock device_lock/hash_lock. Since I
> > > > > release lock, I need recheck if I can find the stripe in hash again. So the
> > > > > seqcount locking doesn't simplify things here. I thought the seqlock only fixes
> > > > > one race. Did I miss anything?
> > > >
> > > > Can you order the locks so that you take the hash_lock first, then the
> > > > device_lock? That would be a lot simpler.
> > >
> > > Looks impossible. For example, in handle_active_stripes() we release several
> > > stripes, we can't take hash_lock first.
> >
> > "impossible" just takes a little longer :-)
> >
> > do_release_stripe gets called with only device_lock held. It gets passed an
> > (initially) empty list_head too.
> > If it wants to add the stripe to an inactive list it puts it on the given
> > list_head instead.
> >
> > release_stripe(), after calling do_release_stripe() calls some function to
> > grab the appropriate hash_lock for each stripe in the list_head and add it
> > to that inactive list.
> >
> > release_stripe_list() might collect some stripes from from __release_stripe
> > that need to go on an inactive list. It arranges for them to be put on the
> > right list, with the right lock, next time device_lock is dropped. That
> > might be in handle_active_stripes()
> >
> > activate_bit_delay might similarly collect stripes, which are handled the
> > same way as those collected by release_stripe_list.
> > etc.
> >
> > i.e. the hash_locks protect the various inactive lists. device_lock protects
> > all the others. If we need to add something to an inactive list while
> > holding device_lock we delay until device_lock can be dropped.
>
> Alright, this option works, but we need allocate some spaces, which isn't very
> good for unplug cb. Below is the patch I tested.
>
> Thanks,
> Shaohua
>
> Subject: raid5: relieve lock contention in get_active_stripe()
>
> get_active_stripe() is the last place we have lock contention. It has two
> paths. One is stripe isn't found and new stripe is allocated, the other is
> stripe is found.
>
> The first path basically calls __find_stripe and init_stripe. It accesses
> conf->generation, conf->previous_raid_disks, conf->raid_disks,
> conf->prev_chunk_sectors, conf->chunk_sectors, conf->max_degraded,
> conf->prev_algo, conf->algorithm, the stripe_hashtbl and inactive_list. Except
> stripe_hashtbl and inactive_list, other fields are changed very rarely.
>
> With this patch, we split inactive_list and add new hash locks. Each free
> stripe belongs to a specific inactive list. Which inactive list is determined
> by stripe's lock_hash. Note, even a stripe hasn't a sector assigned, it has a
> lock_hash assigned. Stripe's inactive list is protected by a hash lock, which
> is determined by it's lock_hash too. The lock_hash is derivied from current
> stripe_hashtbl hash, which guarantees any stripe_hashtbl list will be assigned
> to a specific lock_hash, so we can use new hash lock to protect stripe_hashtbl
> list too. The goal of the new hash locks introduced is we can only use the new
> locks in the first path of get_active_stripe(). Since we have several hash
> locks, lock contention is relieved significantly.
>
> The first path of get_active_stripe() accesses other fields, since they are
> changed rarely, changing them now need take conf->device_lock and all hash
> locks. For a slow path, this isn't a problem.
>
> If we need lock device_lock and hash lock, we always lock hash lock first. The
> tricky part is release_stripe and friends. We need take device_lock first.
> Neil's suggestion is we put inactive stripes to a temporary list and readd it
> to inactive_list after device_lock is released. In this way, we add stripes to
> temporary list with device_lock hold and remove stripes from the list with hash
> lock hold. So we don't allow concurrent access to the temporary list, which
> means we need allocate temporary list for all participants of release_stripe.
>
> One downside is free stripes are maintained in their inactive list, they can't
> across between the lists. By default, we have total 256 stripes and 8 lists, so
> each list will have 32 stripes. It's possible one list has free stripe but
> other list hasn't. The chance should be rare because stripes allocation are
> even distributed. And we can always allocate more stripes for cache, several
> mega bytes memory isn't a big deal.
>
> This completely removes the lock contention of the first path of
> get_active_stripe(). It slows down the second code path a little bit though
> because we now need takes two locks, but since the hash lock isn't contended,
> the overhead should be quite small (several atomic instructions). The second
> path of get_active_stripe() (basically sequential write or big request size
> randwrite) still has lock contentions.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> drivers/md/raid5.c | 346 ++++++++++++++++++++++++++++++++++++++++-------------
> drivers/md/raid5.h | 11 +
> 2 files changed, 276 insertions(+), 81 deletions(-)
>
> Index: linux/drivers/md/raid5.c
> ===================================================================
> --- linux.orig/drivers/md/raid5.c 2013-09-05 08:23:42.187851834 +0800
> +++ linux/drivers/md/raid5.c 2013-09-05 12:52:47.581235145 +0800
> @@ -86,6 +86,67 @@ static inline struct hlist_head *stripe_
> return &conf->stripe_hashtbl[hash];
> }
>
> +static inline int stripe_hash_locks_hash(sector_t sect)
> +{
> + return (sect >> STRIPE_SHIFT) & STRIPE_HASH_LOCKS_MASK;
> +}
> +
> +static inline void lock_device_hash_lock(struct r5conf *conf, int hash)
> +{
> + spin_lock_irq(conf->hash_locks + hash);
> + spin_lock(&conf->device_lock);
> +}
> +
> +static inline void unlock_device_hash_lock(struct r5conf *conf, int hash)
> +{
> + spin_unlock(&conf->device_lock);
> + spin_unlock_irq(conf->hash_locks + hash);
> +}
> +
> +static void __lock_all_hash_locks(struct r5conf *conf)
> +{
> + int i;
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + spin_lock(conf->hash_locks + i);
> +}
> +
> +static void __unlock_all_hash_locks(struct r5conf *conf)
> +{
> + int i;
> + for (i = NR_STRIPE_HASH_LOCKS; i; i--)
> + spin_unlock(conf->hash_locks + i - 1);
> +}
> +
> +static inline void lock_all_device_hash_locks_irq(struct r5conf *conf)
> +{
> + local_irq_disable();
> + __lock_all_hash_locks(conf);
> + spin_lock(&conf->device_lock);
> +}
> +
> +static inline void unlock_all_device_hash_locks_irq(struct r5conf *conf)
> +{
> + spin_unlock(&conf->device_lock);
> + __unlock_all_hash_locks(conf);
> + local_irq_enable();
> +}
> +
> +static inline void lock_all_device_hash_locks_irqsave(struct r5conf *conf,
> + unsigned long *flags)
> +{
> + local_irq_save(*flags);
> + __lock_all_hash_locks(conf);
> + spin_lock(&conf->device_lock);
> +}
> +
> +static inline void unlock_all_device_hash_locks_irqrestore(struct r5conf *conf,
> + unsigned long *flags)
> +{
> + spin_unlock(&conf->device_lock);
> + __unlock_all_hash_locks(conf);
> + local_irq_restore(*flags);
> +}
> +
> /* bio's attached to a stripe+device for I/O are linked together in bi_sector
> * order without overlap. There may be several bio's per stripe+device, and
> * a bio could span several devices.
> @@ -250,7 +311,8 @@ static void raid5_wakeup_stripe_thread(s
> }
> }
>
> -static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh)
> +static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
> + struct list_head *temp_inactive_list)
> {
> BUG_ON(!list_empty(&sh->lru));
> BUG_ON(atomic_read(&conf->active_stripes)==0);
> @@ -279,19 +341,59 @@ static void do_release_stripe(struct r5c
> < IO_THRESHOLD)
> md_wakeup_thread(conf->mddev->thread);
> atomic_dec(&conf->active_stripes);
> - if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
> - list_add_tail(&sh->lru, &conf->inactive_list);
> - wake_up(&conf->wait_for_stripe);
> - if (conf->retry_read_aligned)
> - md_wakeup_thread(conf->mddev->thread);
> - }
> + if (!test_bit(STRIPE_EXPANDING, &sh->state))
> + list_add_tail(&sh->lru, temp_inactive_list);
> }
> }
>
> -static void __release_stripe(struct r5conf *conf, struct stripe_head *sh)
> +static void __release_stripe(struct r5conf *conf, struct stripe_head *sh,
> + struct list_head *temp_inactive_list)
> {
> if (atomic_dec_and_test(&sh->count))
> - do_release_stripe(conf, sh);
> + do_release_stripe(conf, sh, temp_inactive_list);
> +}
> +
> +/*
> + * @hash could be NR_STRIPE_HASH_LOCKS, then we have a list of inactive_list
> + *
> + * Be careful: Only one task can add/delete stripes from temp_inactive_list at
> + * given time. Adding stripes only takes device lock, while deleting stripes
> + * only takes hash lock.
> + */
> +static void release_inactive_stripe_list(struct r5conf *conf,
> + struct list_head *temp_inactive_list, int hash)
> +{
> + int size;
> + bool do_wakeup = false;
> + unsigned long flags;
> +
> + if (hash == NR_STRIPE_HASH_LOCKS) {
> + size = NR_STRIPE_HASH_LOCKS;
> + hash = NR_STRIPE_HASH_LOCKS - 1;
> + } else
> + size = 1;
> + while (size) {
> + struct list_head *list = &temp_inactive_list[size - 1];
> +
> + /*
> + * We don't hold any lock here yet, get_active_stripe() might
> + * remove stripes from the list
> + */
> + if (!list_empty_careful(list)) {
> + spin_lock_irqsave(conf->hash_locks + hash, flags);
> + list_splice_tail_init(list, conf->inactive_list + hash);
> + do_wakeup = true;
> + spin_unlock_irqrestore(conf->hash_locks + hash, flags);
> + }
> + size--;
> + hash--;
> + }
> +
> + if (do_wakeup) {
> + wake_up(&conf->wait_for_stripe);
> + if (conf->retry_read_aligned)
> + md_wakeup_thread(conf->mddev->thread);
> + }
> }
>
> static struct llist_node *llist_reverse_order(struct llist_node *head)
> @@ -309,7 +411,8 @@ static struct llist_node *llist_reverse_
> }
>
> /* should hold conf->device_lock already */
> -static int release_stripe_list(struct r5conf *conf)
> +static int release_stripe_list(struct r5conf *conf,
> + struct list_head *temp_inactive_list)
> {
> struct stripe_head *sh;
> int count = 0;
> @@ -318,6 +421,8 @@ static int release_stripe_list(struct r5
> head = llist_del_all(&conf->released_stripes);
> head = llist_reverse_order(head);
> while (head) {
> + int hash;
> +
> sh = llist_entry(head, struct stripe_head, release_list);
> head = llist_next(head);
> /* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */
> @@ -328,7 +433,8 @@ static int release_stripe_list(struct r5
> * again, the count is always > 1. This is true for
> * STRIPE_ON_UNPLUG_LIST bit too.
> */
> - __release_stripe(conf, sh);
> + hash = sh->hash_lock_index;
> + __release_stripe(conf, sh, &temp_inactive_list[hash]);
> count++;
> }
>
> @@ -339,6 +445,8 @@ static void release_stripe(struct stripe
> {
> struct r5conf *conf = sh->raid_conf;
> unsigned long flags;
> + struct list_head list;
> + int hash;
> bool wakeup;
>
> if (test_and_set_bit(STRIPE_ON_RELEASE_LIST, &sh->state))
> @@ -351,8 +459,11 @@ slow_path:
> local_irq_save(flags);
> /* we are ok here if STRIPE_ON_RELEASE_LIST is set or not */
> if (atomic_dec_and_lock(&sh->count, &conf->device_lock)) {
> - do_release_stripe(conf, sh);
> + INIT_LIST_HEAD(&list);
> + hash = sh->hash_lock_index;
> + do_release_stripe(conf, sh, &list);
> spin_unlock(&conf->device_lock);
> + release_inactive_stripe_list(conf, &list, hash);
> }
> local_irq_restore(flags);
> }
> @@ -377,18 +488,19 @@ static inline void insert_hash(struct r5
>
>
> /* find an idle stripe, make sure it is unhashed, and return it. */
> -static struct stripe_head *get_free_stripe(struct r5conf *conf)
> +static struct stripe_head *get_free_stripe(struct r5conf *conf, int hash)
> {
> struct stripe_head *sh = NULL;
> struct list_head *first;
>
> - if (list_empty(&conf->inactive_list))
> + if (list_empty(conf->inactive_list + hash))
> goto out;
> - first = conf->inactive_list.next;
> + first = (conf->inactive_list + hash)->next;
> sh = list_entry(first, struct stripe_head, lru);
> list_del_init(first);
> remove_hash(sh);
> atomic_inc(&conf->active_stripes);
> + BUG_ON(hash != sh->hash_lock_index);
> out:
> return sh;
> }
> @@ -567,33 +679,35 @@ get_active_stripe(struct r5conf *conf, s
> int previous, int noblock, int noquiesce)
> {
> struct stripe_head *sh;
> + int hash = stripe_hash_locks_hash(sector);
>
> pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
>
> - spin_lock_irq(&conf->device_lock);
> + spin_lock_irq(conf->hash_locks + hash);
>
> do {
> wait_event_lock_irq(conf->wait_for_stripe,
> conf->quiesce == 0 || noquiesce,
> - conf->device_lock);
> + *(conf->hash_locks + hash));
> sh = __find_stripe(conf, sector, conf->generation - previous);
> if (!sh) {
> - if (!conf->inactive_blocked)
> - sh = get_free_stripe(conf);
> + sh = get_free_stripe(conf, hash);
> if (noblock && sh == NULL)
> break;
> if (!sh) {
> conf->inactive_blocked = 1;
> wait_event_lock_irq(conf->wait_for_stripe,
> - !list_empty(&conf->inactive_list) &&
> - (atomic_read(&conf->active_stripes)
> - < (conf->max_nr_stripes *3/4)
> - || !conf->inactive_blocked),
> - conf->device_lock);
> + !list_empty(conf->inactive_list + hash) &&
> + (atomic_read(&conf->active_stripes)
> + < (conf->max_nr_stripes * 3 / 4)
> + || !conf->inactive_blocked),
> + *(conf->hash_locks + hash));
> conf->inactive_blocked = 0;
> } else
> init_stripe(sh, sector, previous);
> } else {
> + spin_lock(&conf->device_lock);
> +
> if (atomic_read(&sh->count)) {
> BUG_ON(!list_empty(&sh->lru)
> && !test_bit(STRIPE_EXPANDING, &sh->state)
> @@ -611,13 +725,14 @@ get_active_stripe(struct r5conf *conf, s
> sh->group = NULL;
> }
> }
> + spin_unlock(&conf->device_lock);
> }
> } while (sh == NULL);
>
> if (sh)
> atomic_inc(&sh->count);
>
> - spin_unlock_irq(&conf->device_lock);
> + spin_unlock_irq(conf->hash_locks + hash);
> return sh;
> }
>
> @@ -1585,7 +1700,7 @@ static void raid_run_ops(struct stripe_h
> put_cpu();
> }
>
> -static int grow_one_stripe(struct r5conf *conf)
> +static int grow_one_stripe(struct r5conf *conf, int hash)
> {
> struct stripe_head *sh;
> sh = kmem_cache_zalloc(conf->slab_cache, GFP_KERNEL);
> @@ -1601,11 +1716,13 @@ static int grow_one_stripe(struct r5conf
> kmem_cache_free(conf->slab_cache, sh);
> return 0;
> }
> + sh->hash_lock_index = hash;
> /* we just created an active stripe so... */
> atomic_set(&sh->count, 1);
> atomic_inc(&conf->active_stripes);
> INIT_LIST_HEAD(&sh->lru);
> release_stripe(sh);
> + conf->max_hash_nr_stripes[hash]++;
> return 1;
> }
>
> @@ -1613,6 +1730,7 @@ static int grow_stripes(struct r5conf *c
> {
> struct kmem_cache *sc;
> int devs = max(conf->raid_disks, conf->previous_raid_disks);
> + int hash;
>
> if (conf->mddev->gendisk)
> sprintf(conf->cache_name[0],
> @@ -1630,9 +1748,12 @@ static int grow_stripes(struct r5conf *c
> return 1;
> conf->slab_cache = sc;
> conf->pool_size = devs;
> - while (num--)
> - if (!grow_one_stripe(conf))
> + hash = 0;
> + while (num--) {
> + if (!grow_one_stripe(conf, hash))
> return 1;
> + hash = (hash + 1) % NR_STRIPE_HASH_LOCKS;
> + }
> return 0;
> }
>
> @@ -1690,6 +1811,7 @@ static int resize_stripes(struct r5conf
> int err;
> struct kmem_cache *sc;
> int i;
> + int hash, cnt;
>
> if (newsize <= conf->pool_size)
> return 0; /* never bother to shrink */
> @@ -1729,19 +1851,28 @@ static int resize_stripes(struct r5conf
> * OK, we have enough stripes, start collecting inactive
> * stripes and copying them over
> */
> + hash = 0;
> + cnt = 0;
> list_for_each_entry(nsh, &newstripes, lru) {
> - spin_lock_irq(&conf->device_lock);
> - wait_event_lock_irq(conf->wait_for_stripe,
> - !list_empty(&conf->inactive_list),
> - conf->device_lock);
> - osh = get_free_stripe(conf);
> - spin_unlock_irq(&conf->device_lock);
> + lock_device_hash_lock(conf, hash);
> + wait_event_cmd(conf->wait_for_stripe,
> + !list_empty(conf->inactive_list + hash),
> + unlock_device_hash_lock(conf, hash),
> + lock_device_hash_lock(conf, hash));
> + osh = get_free_stripe(conf, hash);
> + unlock_device_hash_lock(conf, hash);
> atomic_set(&nsh->count, 1);
> for(i=0; i<conf->pool_size; i++)
> nsh->dev[i].page = osh->dev[i].page;
> for( ; i<newsize; i++)
> nsh->dev[i].page = NULL;
> + nsh->hash_lock_index = hash;
> kmem_cache_free(conf->slab_cache, osh);
> + cnt++;
> + if (cnt >= conf->max_hash_nr_stripes[hash]) {
> + hash++;
> + cnt = 0;
> + }
> }
> kmem_cache_destroy(conf->slab_cache);
>
> @@ -1800,13 +1931,14 @@ static int resize_stripes(struct r5conf
> return err;
> }
>
> -static int drop_one_stripe(struct r5conf *conf)
> +static int drop_one_stripe(struct r5conf *conf, int hash)
> {
> struct stripe_head *sh;
>
> - spin_lock_irq(&conf->device_lock);
> - sh = get_free_stripe(conf);
> - spin_unlock_irq(&conf->device_lock);
> + spin_lock_irq(conf->hash_locks + hash);
> + sh = get_free_stripe(conf, hash);
> + conf->max_hash_nr_stripes[hash]--;
> + spin_unlock_irq(conf->hash_locks + hash);
> if (!sh)
> return 0;
> BUG_ON(atomic_read(&sh->count));
> @@ -1818,8 +1950,10 @@ static int drop_one_stripe(struct r5conf
>
> static void shrink_stripes(struct r5conf *conf)
> {
> - while (drop_one_stripe(conf))
> - ;
> + int hash;
> + for (hash = 0; hash < NR_STRIPE_HASH_LOCKS; hash++)
> + while (drop_one_stripe(conf, hash))
> + ;
>
> if (conf->slab_cache)
> kmem_cache_destroy(conf->slab_cache);
> @@ -2048,10 +2182,10 @@ static void error(struct mddev *mddev, s
> unsigned long flags;
> pr_debug("raid456: error called\n");
>
> - spin_lock_irqsave(&conf->device_lock, flags);
> + lock_all_device_hash_locks_irqsave(conf, &flags);
> clear_bit(In_sync, &rdev->flags);
> mddev->degraded = calc_degraded(conf);
> - spin_unlock_irqrestore(&conf->device_lock, flags);
> + unlock_all_device_hash_locks_irqrestore(conf, &flags);
> set_bit(MD_RECOVERY_INTR, &mddev->recovery);
>
> set_bit(Blocked, &rdev->flags);
> @@ -3895,7 +4029,8 @@ static void raid5_activate_delayed(struc
> }
> }
>
> -static void activate_bit_delay(struct r5conf *conf)
> +static void activate_bit_delay(struct r5conf *conf,
> + struct list_head *temp_inactive_list)
> {
> /* device_lock is held */
> struct list_head head;
> @@ -3903,9 +4038,11 @@ static void activate_bit_delay(struct r5
> list_del_init(&conf->bitmap_list);
> while (!list_empty(&head)) {
> struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
> + int hash;
> list_del_init(&sh->lru);
> atomic_inc(&sh->count);
> - __release_stripe(conf, sh);
> + hash = sh->hash_lock_index;
> + __release_stripe(conf, sh, &temp_inactive_list[hash]);
> }
> }
>
> @@ -3921,7 +4058,7 @@ int md_raid5_congested(struct mddev *mdd
> return 1;
> if (conf->quiesce)
> return 1;
> - if (list_empty_careful(&conf->inactive_list))
> + if (atomic_read(&conf->active_stripes) == conf->max_nr_stripes)
> return 1;
>
> return 0;
> @@ -4251,6 +4388,7 @@ static struct stripe_head *__get_priorit
> struct raid5_plug_cb {
> struct blk_plug_cb cb;
> struct list_head list;
> + struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
> };
>
> static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
> @@ -4261,6 +4399,7 @@ static void raid5_unplug(struct blk_plug
> struct mddev *mddev = cb->cb.data;
> struct r5conf *conf = mddev->private;
> int cnt = 0;
> + int hash;
>
> if (cb->list.next && !list_empty(&cb->list)) {
> spin_lock_irq(&conf->device_lock);
> @@ -4278,11 +4417,14 @@ static void raid5_unplug(struct blk_plug
> * STRIPE_ON_RELEASE_LIST could be set here. In that
> * case, the count is always > 1 here
> */
> - __release_stripe(conf, sh);
> + hash = sh->hash_lock_index;
> + __release_stripe(conf, sh, &cb->temp_inactive_list[hash]);
> cnt++;
> }
> spin_unlock_irq(&conf->device_lock);
> }
> + release_inactive_stripe_list(conf, cb->temp_inactive_list,
> + NR_STRIPE_HASH_LOCKS);
> if (mddev->queue)
> trace_block_unplug(mddev->queue, cnt, !from_schedule);
> kfree(cb);
> @@ -4303,8 +4445,12 @@ static void release_stripe_plug(struct m
>
> cb = container_of(blk_cb, struct raid5_plug_cb, cb);
>
> - if (cb->list.next == NULL)
> + if (cb->list.next == NULL) {
> + int i;
> INIT_LIST_HEAD(&cb->list);
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + INIT_LIST_HEAD(cb->temp_inactive_list + i);
> + }
>
> if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))
> list_add_tail(&sh->lru, &cb->list);
> @@ -4949,27 +5095,45 @@ static int retry_aligned_read(struct r5
> }
>
> static int handle_active_stripes(struct r5conf *conf, int group,
> - struct r5worker *worker)
> + struct r5worker *worker,
> + struct list_head *temp_inactive_list)
> {
> struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
> - int i, batch_size = 0;
> + int i, batch_size = 0, hash;
> + bool release_inactive = false;
>
> while (batch_size < MAX_STRIPE_BATCH &&
> (sh = __get_priority_stripe(conf, group)) != NULL)
> batch[batch_size++] = sh;
>
> - if (batch_size == 0)
> - return batch_size;
> + if (batch_size == 0) {
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + if (!list_empty(temp_inactive_list + i))
> + break;
> + if (i == NR_STRIPE_HASH_LOCKS)
> + return batch_size;
> + release_inactive = true;
> + }
> spin_unlock_irq(&conf->device_lock);
>
> + release_inactive_stripe_list(conf, temp_inactive_list,
> + NR_STRIPE_HASH_LOCKS);
> +
> + if (release_inactive) {
> + spin_lock_irq(&conf->device_lock);
> + return 0;
> + }
> +
> for (i = 0; i < batch_size; i++)
> handle_stripe(batch[i]);
>
> cond_resched();
>
> spin_lock_irq(&conf->device_lock);
> - for (i = 0; i < batch_size; i++)
> - __release_stripe(conf, batch[i]);
> + for (i = 0; i < batch_size; i++) {
> + hash = batch[i]->hash_lock_index;
> + __release_stripe(conf, batch[i], &temp_inactive_list[hash]);
> + }
> return batch_size;
> }
>
> @@ -4990,9 +5154,10 @@ static void raid5_do_work(struct work_st
> while (1) {
> int batch_size, released;
>
> - released = release_stripe_list(conf);
> + released = release_stripe_list(conf, worker->temp_inactive_list);
>
> - batch_size = handle_active_stripes(conf, group_id, worker);
> + batch_size = handle_active_stripes(conf, group_id, worker,
> + worker->temp_inactive_list);
> worker->working = false;
> if (!batch_size && !released)
> break;
> @@ -5031,7 +5196,7 @@ static void raid5d(struct md_thread *thr
> struct bio *bio;
> int batch_size, released;
>
> - released = release_stripe_list(conf);
> + released = release_stripe_list(conf, conf->temp_inactive_list);
>
> if (
> !list_empty(&conf->bitmap_list)) {
> @@ -5041,7 +5206,7 @@ static void raid5d(struct md_thread *thr
> bitmap_unplug(mddev->bitmap);
> spin_lock_irq(&conf->device_lock);
> conf->seq_write = conf->seq_flush;
> - activate_bit_delay(conf);
> + activate_bit_delay(conf, conf->temp_inactive_list);
> }
> raid5_activate_delayed(conf);
>
> @@ -5055,7 +5220,8 @@ static void raid5d(struct md_thread *thr
> handled++;
> }
>
> - batch_size = handle_active_stripes(conf, ANY_GROUP, NULL);
> + batch_size = handle_active_stripes(conf, ANY_GROUP, NULL,
> + conf->temp_inactive_list);
> if (!batch_size && !released)
> break;
> handled += batch_size;
> @@ -5091,22 +5257,28 @@ raid5_set_cache_size(struct mddev *mddev
> {
> struct r5conf *conf = mddev->private;
> int err;
> + int hash;
>
> if (size <= 16 || size > 32768)
> return -EINVAL;
> + size = round_up(size, NR_STRIPE_HASH_LOCKS);
> + hash = 0;
> while (size < conf->max_nr_stripes) {
> - if (drop_one_stripe(conf))
> + if (drop_one_stripe(conf, hash))
> conf->max_nr_stripes--;
> else
> break;
> + hash = (hash + 1) % NR_STRIPE_HASH_LOCKS;
> }
> err = md_allow_write(mddev);
> if (err)
> return err;
> + hash = 0;
> while (size > conf->max_nr_stripes) {
> - if (grow_one_stripe(conf))
> + if (grow_one_stripe(conf, hash))
> conf->max_nr_stripes++;
> else break;
> + hash = (hash + 1) % NR_STRIPE_HASH_LOCKS;
> }
> return 0;
> }
> @@ -5257,7 +5429,7 @@ static struct attribute_group raid5_attr
>
> static int alloc_thread_groups(struct r5conf *conf, int cnt)
> {
> - int i, j;
> + int i, j, k;
> ssize_t size;
> struct r5worker *workers;
>
> @@ -5287,8 +5459,12 @@ static int alloc_thread_groups(struct r5
> group->workers = workers + i * cnt;
>
> for (j = 0; j < cnt; j++) {
> - group->workers[j].group = group;
> - INIT_WORK(&group->workers[j].work, raid5_do_work);
> + struct r5worker *worker = group->workers + j;
> + worker->group = group;
> + INIT_WORK(&worker->work, raid5_do_work);
> +
> + for (k = 0; k < NR_STRIPE_HASH_LOCKS; k++)
> + INIT_LIST_HEAD(worker->temp_inactive_list + k);
> }
> }
>
> @@ -5439,6 +5615,7 @@ static struct r5conf *setup_conf(struct
> struct md_rdev *rdev;
> struct disk_info *disk;
> char pers_name[6];
> + int i;
>
> if (mddev->new_level != 5
> && mddev->new_level != 4
> @@ -5483,7 +5660,6 @@ static struct r5conf *setup_conf(struct
> INIT_LIST_HEAD(&conf->hold_list);
> INIT_LIST_HEAD(&conf->delayed_list);
> INIT_LIST_HEAD(&conf->bitmap_list);
> - INIT_LIST_HEAD(&conf->inactive_list);
> init_llist_head(&conf->released_stripes);
> atomic_set(&conf->active_stripes, 0);
> atomic_set(&conf->preread_active_stripes, 0);
> @@ -5509,6 +5685,15 @@ static struct r5conf *setup_conf(struct
> if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
> goto abort;
>
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + spin_lock_init(conf->hash_locks + i);
> +
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + INIT_LIST_HEAD(conf->inactive_list + i);
> +
> + for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
> + INIT_LIST_HEAD(conf->temp_inactive_list + i);
> +
> conf->level = mddev->new_level;
> if (raid5_alloc_percpu(conf) != 0)
> goto abort;
> @@ -6034,9 +6219,9 @@ static int raid5_spare_active(struct mdd
> sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
> }
> }
> - spin_lock_irqsave(&conf->device_lock, flags);
> + lock_all_device_hash_locks_irqsave(conf, &flags);
> mddev->degraded = calc_degraded(conf);
> - spin_unlock_irqrestore(&conf->device_lock, flags);
> + unlock_all_device_hash_locks_irqrestore(conf, &flags);
> print_raid5_conf(conf);
> return count;
> }
> @@ -6347,9 +6532,9 @@ static int raid5_start_reshape(struct md
> * ->degraded is measured against the larger of the
> * pre and post number of devices.
> */
> - spin_lock_irqsave(&conf->device_lock, flags);
> + lock_all_device_hash_locks_irqsave(conf, &flags);
> mddev->degraded = calc_degraded(conf);
> - spin_unlock_irqrestore(&conf->device_lock, flags);
> + unlock_all_device_hash_locks_irqrestore(conf, &flags);
> }
> mddev->raid_disks = conf->raid_disks;
> mddev->reshape_position = conf->reshape_progress;
> @@ -6363,14 +6548,14 @@ static int raid5_start_reshape(struct md
> "reshape");
> if (!mddev->sync_thread) {
> mddev->recovery = 0;
> - spin_lock_irq(&conf->device_lock);
> + lock_all_device_hash_locks_irq(conf);
> mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
> rdev_for_each(rdev, mddev)
> rdev->new_data_offset = rdev->data_offset;
> smp_wmb();
> conf->reshape_progress = MaxSector;
> mddev->reshape_position = MaxSector;
> - spin_unlock_irq(&conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf);
> return -EAGAIN;
> }
> conf->reshape_checkpoint = jiffies;
> @@ -6388,13 +6573,13 @@ static void end_reshape(struct r5conf *c
> if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
> struct md_rdev *rdev;
>
> - spin_lock_irq(&conf->device_lock);
> + lock_all_device_hash_locks_irq(conf);
> conf->previous_raid_disks = conf->raid_disks;
> rdev_for_each(rdev, conf->mddev)
> rdev->data_offset = rdev->new_data_offset;
> smp_wmb();
> conf->reshape_progress = MaxSector;
> - spin_unlock_irq(&conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf);
> wake_up(&conf->wait_for_overlap);
>
> /* read-ahead size must cover two whole stripes, which is
> @@ -6425,9 +6610,9 @@ static void raid5_finish_reshape(struct
> revalidate_disk(mddev->gendisk);
> } else {
> int d;
> - spin_lock_irq(&conf->device_lock);
> + lock_all_device_hash_locks_irq(conf);
> mddev->degraded = calc_degraded(conf);
> - spin_unlock_irq(&conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf);
> for (d = conf->raid_disks ;
> d < conf->raid_disks - mddev->delta_disks;
> d++) {
> @@ -6457,27 +6642,28 @@ static void raid5_quiesce(struct mddev *
> break;
>
> case 1: /* stop all writes */
> - spin_lock_irq(&conf->device_lock);
> + lock_all_device_hash_locks_irq(conf);
> /* '2' tells resync/reshape to pause so that all
> * active stripes can drain
> */
> conf->quiesce = 2;
> - wait_event_lock_irq(conf->wait_for_stripe,
> + wait_event_cmd(conf->wait_for_stripe,
> atomic_read(&conf->active_stripes) == 0 &&
> atomic_read(&conf->active_aligned_reads) == 0,
> - conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf),
> + lock_all_device_hash_locks_irq(conf));
> conf->quiesce = 1;
> - spin_unlock_irq(&conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf);
> /* allow reshape to continue */
> wake_up(&conf->wait_for_overlap);
> break;
>
> case 0: /* re-enable writes */
> - spin_lock_irq(&conf->device_lock);
> + lock_all_device_hash_locks_irq(conf);
> conf->quiesce = 0;
> wake_up(&conf->wait_for_stripe);
> wake_up(&conf->wait_for_overlap);
> - spin_unlock_irq(&conf->device_lock);
> + unlock_all_device_hash_locks_irq(conf);
> break;
> }
> }
> Index: linux/drivers/md/raid5.h
> ===================================================================
> --- linux.orig/drivers/md/raid5.h 2013-09-05 08:23:42.187851834 +0800
> +++ linux/drivers/md/raid5.h 2013-09-05 08:30:49.090484930 +0800
> @@ -205,6 +205,7 @@ struct stripe_head {
> short pd_idx; /* parity disk index */
> short qd_idx; /* 'Q' disk index for raid6 */
> short ddf_layout;/* use DDF ordering to calculate Q */
> + short hash_lock_index;
> unsigned long state; /* state flags */
> atomic_t count; /* nr of active thread/requests */
> int bm_seq; /* sequence number for bitmap flushes */
> @@ -367,9 +368,13 @@ struct disk_info {
> struct md_rdev *rdev, *replacement;
> };
>
> +#define NR_STRIPE_HASH_LOCKS 8
> +#define STRIPE_HASH_LOCKS_MASK (NR_STRIPE_HASH_LOCKS - 1)
> +
> struct r5worker {
> struct work_struct work;
> struct r5worker_group *group;
> + struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
> bool working;
> };
>
> @@ -382,6 +387,8 @@ struct r5worker_group {
>
> struct r5conf {
> struct hlist_head *stripe_hashtbl;
> + /* only protect corresponding hash list and inactive_list */
> + spinlock_t hash_locks[NR_STRIPE_HASH_LOCKS];
> struct mddev *mddev;
> int chunk_sectors;
> int level, algorithm;
> @@ -462,7 +469,8 @@ struct r5conf {
> * Free stripes pool
> */
> atomic_t active_stripes;
> - struct list_head inactive_list;
> + struct list_head inactive_list[NR_STRIPE_HASH_LOCKS];
> + int max_hash_nr_stripes[NR_STRIPE_HASH_LOCKS];
> struct llist_head released_stripes;
> wait_queue_head_t wait_for_stripe;
> wait_queue_head_t wait_for_overlap;
> @@ -477,6 +485,7 @@ struct r5conf {
> * the new thread here until we fully activate the array.
> */
> struct md_thread *thread;
> + struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
> struct r5worker_group *worker_groups;
> int group_cnt;
> int worker_cnt_per_group;
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi,
thanks for this. It is looking quite good.
I don't really like max_hash_nr_stripes though.
I note that you round up the cache_size to a multiple of
NR_STRIPE_HASH_LOCKS.
I think that is a good idea and should allow us to ensure that every hash
value always has the same number of stripe_heads.
If we get a failure when allocating, we would need to free some to bring it
back to a uniform number.
I'm in two minds about the temp_inactive_list.
An alternative would be to have a single list and use list_sort() to sort it
by hash_lock_index before moving the stripe_heads to the relevant lists,
taking one lock at a time.
This save some memory and costs some cpu time. On the whole I think it
gains in elegance but I'm not sure. What do you think?
Thanks,
NeilBrown
Attachment:
signature.asc
Description: PGP signature
