On Thu, 12 Sep 2013 09:55:07 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> On Wed, Sep 11, 2013 at 11:34:12AM +1000, NeilBrown wrote:
> > On Tue, 10 Sep 2013 15:37:56 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> >
> >
> > > Below is my latest patch.
> > >
> >
> > Thanks. It looks good.
> > I have pushed it out to me for-next branch (which a few cosmetic white-space
> > adjustments).
> > I will need to review it again but it is certainly very close to 'right'.
> >
> > One thing I'm a bit concerned about is the md_raid5_congested function.
> > It can return "false", yet a write can still block.
> > That isn't a huge problem, but it could have some negative consequences.
> > Maybe we could have an atomic_t which counts how many hash values as "full"
> > and we report "congested" when any are full. Maybe.
>
> Since there is no overhead in hot code patch, I agree. Here is the patch:
>
>
> Subject: raid5: track empty inactive list count
>
> track empty inactive list count, so md_raid5_congested() can use it to make
> decision.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> drivers/md/raid5.c | 8 +++++++-
> drivers/md/raid5.h | 1 +
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> Index: linux/drivers/md/raid5.c
> ===================================================================
> --- linux.orig/drivers/md/raid5.c 2013-09-12 08:31:07.740146654 +0800
> +++ linux/drivers/md/raid5.c 2013-09-12 09:49:32.816360986 +0800
> @@ -355,6 +355,9 @@ static void release_inactive_stripe_list
> */
> if (!list_empty_careful(list)) {
> spin_lock_irqsave(conf->hash_locks + hash, flags);
> + if (list_empty(conf->inactive_list + hash) &&
> + !list_empty(list))
> + atomic_dec(&conf->empty_inactive_list_nr);
> list_splice_tail_init(list, conf->inactive_list + hash);
> do_wakeup = true;
> spin_unlock_irqrestore(conf->hash_locks + hash, flags);
> @@ -475,6 +478,8 @@ static struct stripe_head *get_free_stri
> remove_hash(sh);
> atomic_inc(&conf->active_stripes);
> BUG_ON(hash != sh->hash_lock_index);
> + if (list_empty(conf->inactive_list + hash))
> + atomic_inc(&conf->empty_inactive_list_nr);
> out:
> return sh;
> }
> @@ -4035,7 +4040,7 @@ int md_raid5_congested(struct mddev *mdd
> return 1;
> if (conf->quiesce)
> return 1;
> - if (atomic_read(&conf->active_stripes) == conf->max_nr_stripes)
> + if (atomic_read(&conf->empty_inactive_list_nr))
> return 1;
>
> return 0;
> @@ -5721,6 +5726,7 @@ static struct r5conf *setup_conf(struct
>
> memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
> max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
> + atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);
> if (grow_stripes(conf, NR_STRIPES)) {
> printk(KERN_ERR
> "md/raid:%s: couldn't allocate %dkB for buffers\n",
> Index: linux/drivers/md/raid5.h
> ===================================================================
> --- linux.orig/drivers/md/raid5.h 2013-09-12 08:31:07.740146654 +0800
> +++ linux/drivers/md/raid5.h 2013-09-12 08:33:45.666153078 +0800
> @@ -470,6 +470,7 @@ struct r5conf {
> */
> atomic_t active_stripes;
> struct list_head inactive_list[NR_STRIPE_HASH_LOCKS];
> + atomic_t empty_inactive_list_nr;
> struct llist_head released_stripes;
> wait_queue_head_t wait_for_stripe;
> wait_queue_head_t wait_for_overlap;
Thanks. Applied.
NeilBrown
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