Re: Can't resgister cache

[Franco <franco-uJ2R6605E/fKnmoGZ802fQ@public.gmane.org>]

I did a reboot and got it registered again.

bio: create slab <bio-1> at 1
bcache: invalidating existing data
bcache: registered cache device sdb
bcache: Caching sdc, inserted new UUID 87ba7904-7690-4985-b6a8-daeba41712a3
EXT4-fs (bcache0): mounted filesystem with ordered data mode. Opts: (null)


First read went at 119 MB/Sec, second at 37MB/Sec

Here's what's in stats_hour

/sys/block/sdc/bcache/stats_hour/cache_bypass_hits
::::::::::::::
44
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_bypass_misses
::::::::::::::
81172
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_hit_ratio
::::::::::::::
0
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_hits
::::::::::::::
24
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_miss_collisions
::::::::::::::
14
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_misses
::::::::::::::
407422
::::::::::::::
/sys/block/sdc/bcache/stats_hour/cache_readaheads
::::::::::::::
0

With echo 0 >/sys/block/sdc/bcache/sequential_cutoff

33 MB/Sec


On Tue, 2012-02-14 at 22:24 -0800, Kent Overstreet wrote: 
> Not sure what's going on with not being able to register again - not a
> lot of info to go off of. It was working last I checked in the
> bcache-3.2-dev branch, it might be buggy in the older bcache branch.
> 
> >From your numbers it looks like the 8 gb of data wasn't in the cache -
> bcache bypasses sequential IO by default. You can flip it off by
> echoing 0 to sequential_cutoff.
> 
> On Tue, Feb 14, 2012 at 9:26 PM, Franco <franco-uJ2R6605E/fKnmoGZ802fQ@public.gmane.org> wrote:
> > Hi
> >
> > I was in the process of testing linux-bcache but was seeing some strange
> > behaviour so I thought I would remount my cached filesystem. I then
> > noticed that the performance results started looking like the cache just
> > wasn't there, so I unregistered it:
> >
> > bcache: Cache set be008612-38aa-4082-9f42-1bada25cb002 unregistered
> > bcache: Caching disabled for sdc
> >
> > but now when I try to register it again, I get bcache: error
> > opening /dev/sdb: device busy.
> >
> > I haven't tried rebooting yet but probably will do after I've sent this
> > message.
> >
> > These were the strange results I was getting that prompted me to unmount
> > and remount the filesystems.
> >
> > Setup: hardware RAID 5 16 disk array with 2 partitions, 1 Intel 40GB SSD
> > for bcache.
> >
> > Filesystem            Size  Used Avail Use% Mounted on
> > /dev/bcache0          1.9T   26G  1.8T   2% /data33
> > /dev/sdd              1.9T   23G  1.8T   2% /data34
> >
> > Wrote an 8GB file to each filesystem, then tried reading it back.
> > Machine has 8GB RAM.
> >
> > Speed for random reads from identical SSD = 181.766523 MB/Sec, random
> > read test done in the following order with measured speed in MB/Sec. The
> > random IO is actually just reading with a 4GB stride, wrapping around at
> > the end of the file.
> >
> > /data33 49
> > /data34 114
> > /data33 114
> > /data33 and /data44 simultaneously 78 and 59 respectively
> > /data33 76
> > /data33 68
> > /data34 114
> > /data34 96
> > /data34 69
> > /data34 74
> > /data33 118
> > /data33 40
> > /data34 91
> >
> > After remounting both filesystems:
> >
> > /data34 148
> > /data33 120
> > /data34 120
> > /data33 82
> >
> >
> > After unregistering the cache
> >
> > /data33 65
> > /data34 83
> > /data33 99
> > /data34 113
> >
> > Cheers,
> > Franco
> >
> >
> > --
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