Hi Kent, After some test, we saw log in dmesg like below:
[ 1505.282400] bcache: bch_allocator_thread() bcache: invalidating buckets: free_inc 0/127 [ 1505.285843] bcache: bch_allocator_thread() bcache: not writing prios: free_inc 0/127 [ 1508.005957] bcache: bch_allocator_thread() bcache: invalidating buckets: free_inc 0/127 [ 1508.009357] bcache: bch_allocator_thread() bcache: not writing prios: free_inc 0/127 [ 1512.493609] bcache: bch_allocator_thread() bcache: invalidating buckets: free_inc 0/127 [ 1512.497070] bcache: bch_allocator_thread() bcache: not writing prios: free_inc 0/127 Does this show some clue to you? Regards, Jack On 04/22/2013 11:51 PM, Kent Overstreet wrote: > On Mon, Apr 22, 2013 at 10:27:03PM +0200, Jack Wang wrote: >> Thanks for reply, Kent, two of my colleagues saw this behaviour, so I >> think we can reproduce this. >> If you could give me more detailed guide to narrow it down, I can try it >> on my side. > > So, my current hypothesis is that the problem is the allocator spinning, > and the IO is from it continually rewriting prios/gens. > > But I'm still not sure what's causing the allocator to spin, that's what > the last patch was supposed to fix. > > Can you see if you can reproduce it with this patch, and then tell me > what shows up in the dmesg log? I expect you'll get a _lot_ of output - > flip timestamps on in your kernel config, if they're not already on. > Thanks! > > commit 60a09d37d301f88dd0f0f413408821a067966d1a > Author: Kent Overstreet <[email protected]> > Date: Mon Apr 22 14:49:33 2013 -0700 > > bcache: Allocator debug patch > > diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c > index 2879487..37c22c6 100644 > --- a/drivers/md/bcache/alloc.c > +++ b/drivers/md/bcache/alloc.c > @@ -393,12 +393,15 @@ void bch_allocator_thread(struct closure *cl) > allocator_wait(ca, !list_empty(&ca->discards)); > do_discard(ca, bucket); > } else { > - fifo_push(&ca->free, bucket); > + BUG_ON(!fifo_push(&ca->free, bucket)); > closure_wake_up(&ca->set->bucket_wait); > } > } > > allocator_wait(ca, ca->set->gc_mark_valid); > + > + printk(KERN_DEBUG "bcache: invalidating buckets: free_inc > %zu/%zu\n", > + fifo_used(&ca->free_inc), ca->free_inc.size); > invalidate_buckets(ca); > > allocator_wait(ca, !atomic_read(&ca->set->prio_blocked) || > @@ -407,8 +410,12 @@ void bch_allocator_thread(struct closure *cl) > if (CACHE_SYNC(&ca->set->sb) && > (!fifo_empty(&ca->free_inc) || > ca->need_save_prio > 64)) { > + printk(KERN_DEBUG "bcache: writing prios: free_inc > %zu/%zu\n", > + fifo_used(&ca->free_inc), ca->free_inc.size); > bch_prio_write(ca); > - } > + } else > + printk(KERN_DEBUG "bcache: not writing prios: free_inc > %zu/%zu\n", > + fifo_used(&ca->free_inc), ca->free_inc.size); > } > } > -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
