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;
--
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