That would probably have helped. The XFS deadlocks would only occur when there was relatively little free memory. Kernel 3.18 is supposed to have a fix for that, but I haven't tried it yet.
Looking at my actual usage, I don't even need 64k inodes. 64k inodes should make things a bit faster when you have a large number of files in a directory. Ceph will automatically split directories with too many files into multiple sub-directories, so it's kinda pointless.
I may try the experiment again, but probably not. It took several weeks to reformat all of the OSDS. Even on a single node, it takes 4-5 days to drain, format, and backfill. That was months ago, and I'm still dealing with the side effects. I'm not eager to try again.
On Mon, Nov 17, 2014 at 2:04 PM, Andrey Korolyov <andrey@xxxxxxx> wrote:
On Tue, Nov 18, 2014 at 12:54 AM, Craig Lewis <clewis@xxxxxxxxxxxxxxxxxx> wrote:
> I did have a problem in my secondary cluster that sounds similar to yours.
> I was using XFS, and traced my problem back to 64 kB inodes (osd mkfs
> options xfs = -i size=64k). This showed up with a lot of "XFS: possible
> memory allocation deadlock in kmem_alloc" in the kernel logs. I was able to
> keep things limping along by flushing the cache frequently, but I eventually
> re-formatted every OSD to get rid of the 64k inodes.
>
> After I finished the reformat, I had problems because of deep-scrubbing.
> While reformatting, I disabled deep-scrubbing. Once I re-enabled it, Ceph
> wanted to deep-scrub the whole cluster, and sometimes 90% of my OSDs would
> be doing a deep-scrub. I'm manually deep-scrubbing now, trying to spread
> out the schedule a bit. Once this finishes in a few day, I should be able
> to re-enable deep-scrubbing and keep my HEALTH_OK.
>
>
Would you mind to check suggestions by following mine hints or hints
from mentioned URLs from there
http://marc.info/?l=linux-mm&m=141607712831090&w=2 with 64k again? As
for me, I am not observing lock loop after setting min_free_kbytes for
a half of gigabyte per OSD. Even if your locks has a different nature,
it may be worthy to try anyway.
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