Re: spinning kworker with space_cache=v2 searching for free space

[Liu Bo <bo.li.liu@oracle.com>]

On Wed, Nov 09, 2016 at 09:19:21PM +0100, Stefan Priebe - Profihost AG wrote:
> Hello,
> 
> found this one from 2014:
> https://patchwork.kernel.org/patch/5551651/
> 
> it this still valid?

The space cache code doesn't change a lot, so I think the patch is still
valid to apply(there might be some conflicts though), but I'm not sure
if it could help the spinning case.

Thanks,

-liubo
> 
> Am 09.11.2016 um 09:09 schrieb Stefan Priebe - Profihost AG:
> > Dear list,
> > 
> > even there's a lot of free space on my disk:
> > 
> > # df -h /vmbackup/
> > Filesystem                    Size  Used Avail Use% Mounted on
> > /dev/mapper/stripe0-backup   37T   24T   13T  64% /backup
> > 
> > # btrfs filesystem df /backup/
> > Data, single: total=23.75TiB, used=22.83TiB
> > System, DUP: total=8.00MiB, used=3.94MiB
> > Metadata, DUP: total=283.50GiB, used=105.82GiB
> > GlobalReserve, single: total=512.00MiB, used=0.00B
> > 
> > I always have a kworker process endless spinning.
> > 
> > # perf top shows:
> >   47,56%  [kernel]               [k] rb_next
> >    7,71%  [kernel]               [k] tree_search_offset.isra.25
> >    6,44%  [kernel]               [k] btrfs_find_space_for_alloc
> > 
> > Mount options:
> > rw,noatime,compress-force=zlib,nossd,noacl,space_cache=v2,skip_balance
> > 
> > What's wrong here?
> > 
> > Greets,
> > Stefan
> >