Seg fault in blkparse.

I recorded a 3 minutes of heavy IO (generated with fio) with:
blktrace -w 240 -a read -a write -a fs -I devs -o btrfs-12-blk.log

(I used 240 seconds to make sure I didn't miss any of the 180 seconds of I/O).

As a small aside I wasn't sure what the default filter mask was, it seems more correct to use:
blktrace -w 240 -A read -a write -a fs -I devs -o btrfs-12-blk.log

So set the mask to exactly (and only) read, then add write, and fs. But that dies with:

    Invalid set action mask read/0x0

The above mentioned file "devs" contains /etc/sdc1 ... /dev/sdn1 (12 devices, one per line).

It generated 16 log files (it's a dual socket x quad core/8 thread intel CPUs). The logs total 15M (using du --total -h *blktrace*).

blkparse reliably seg faults at around 102 seconds into the log:

   8,209  1     5749   102.246254903  4825  U   N [(null)] 2
   8,113  4    10445   102.255427790     0  C   R 14356151 + 8 [10445]

Segmentation fault

Stderror does have some strange output:

# blkparse btrfs-12-blk.log > /dev/null
Bad magic 0
Bad magic 0
Bad magic 0
Bad magic 8
Bad magic 0
Bad magic 0
Bad magic 0
Bad magic c2d3ccfa
Segmentation fault

It generated 61,758 lines of output when it dies.

Additional information about this machine, it's an ubuntu 11.04 x86-64 machine with:

# uname -a
Linux fb 2.6.38-8-server #42-Ubuntu SMP Mon Apr 11 03:49:04 UTC 2011 
x86_64 x86_64 x86_64 GNU/Linux
# blkparse --version
blkparse version 1.0.1
# blktrace --version
blktrace version 2.0.0

This doesn't seem like a particularly challenging log to handle.

I looked for a way to tell blkparse to use a larger buffer but I didn't see a way to do that with blkparse --help or the blkparse man page.

Stupid user error? Suggestions? I'm sending it to this list as directed by the man page.

would you mind providing a tar.gz for the btrfs-12-blk.log?

Regards,
Tao

Sure. I did have the log from the previous run, but I was careful in reproducing it and I get a slightly different result:

# blkparse rand-read-btrfs-r1-blk.log | wc -l
Bad magic 0
Bad magic 0
Bad magic 0
Bad magic 0
Out of memory, CPU info for device rand-read-btrfs-r1- (-46513984)

Which brings up another question. I setup a btrfs with 12 32GB partitions:

# btrfs filesystem show
failed to read /dev/sr0
Label: none  uuid: 16c43865-52d8-42ec-a0c3-420f0184f622
	Total devices 12 FS bytes used 96.12GB
	devid    2 size 32.00GB used 32.00GB path /dev/sdd1
	devid    3 size 32.00GB used 32.00GB path /dev/sde1
	devid    5 size 32.00GB used 32.00GB path /dev/sdg1
	devid    6 size 32.00GB used 32.00GB path /dev/sdh1
	devid   11 size 32.00GB used 32.00GB path /dev/sdm1
	devid    8 size 32.00GB used 32.00GB path /dev/sdj1
	devid   10 size 32.00GB used 32.00GB path /dev/sdl1
	devid   12 size 32.00GB used 32.00GB path /dev/sdn1
	devid    1 size 32.00GB used 32.00GB path /dev/sdc1
	devid    4 size 32.00GB used 32.00GB path /dev/sdf1
	devid    9 size 32.00GB used 32.00GB path /dev/sdk1
	devid    7 size 32.00GB used 32.00GB path /dev/sdi1

But there's no specific device for it, so I can mount any of the devices (/dev/sd[cdefghijklmn]1) and see the entire volume:

$ df -h /tank
Filesystem            Size  Used Avail Use% Mounted on
/dev/sdc1             385G  193G  191G  51% /tank

So obvious the btrfs mounted with /dev/sdc1 (385GB across 12 disks) is not the same as the device /dev/sdc1 (a 32GB partition on a single disk).

So for proper btrfs usage I should monitor /dev/sdc1? Use 12 -d's to add each device? Use -I and list the 12 devices one per line in a file?

Oh, the requests logs as well as details for making the filesystem, running the benchmark, and recording the blktrace is a 5.1MB file at
http://broadley.org/bill/blktrace-btrfs.tar.gz

Sorry for the confusion.

Some small fixes.

I didn't have the logs so I had to reproduce them.

I meant for proper blktrace usage, not btrfs