bad performance on touch/cp file on XFS system

[Zhang Qiang]

Dear XFS community & developers,

I am using CentOS 6.3 and xfs as base file system and use RAID5 as hardware
storage.

Detail environment as follow:
   OS: CentOS 6.3
   Kernel: kernel-2.6.32-279.el6.x86_64
   XFS option info(df output): /dev/sdb1 on /data type xfs
(rw,noatime,nodiratime,nobarrier)

Detail phenomenon:

    # df
    Filesystem            Size  Used Avail Use% Mounted on
    /dev/sda1              29G   17G   11G  61% /
    /dev/sdb1             893G  803G   91G  90% /data
    /dev/sda4             2.2T  1.6T  564G  75% /data1

    # time touch /data1/1111
    real    0m23.043s
    user    0m0.001s
    sys     0m0.349s

    # perf top
    Events: 6K cycles
     16.96%  [xfs]                     [k] xfs_inobt_get_rec
     11.95%  [xfs]                     [k] xfs_btree_increment
     11.16%  [xfs]                     [k] xfs_btree_get_rec
      7.39%  [xfs]                     [k] xfs_btree_get_block
      5.02%  [xfs]                     [k] xfs_dialloc
      4.87%  [xfs]                     [k] xfs_btree_rec_offset
      4.33%  [xfs]                     [k] xfs_btree_readahead
      4.13%  [xfs]                     [k] _xfs_buf_find
      4.05%  [kernel]                  [k] intel_idle
      2.89%  [xfs]                     [k] xfs_btree_rec_addr
      1.04%  [kernel]                  [k] kmem_cache_free


It seems that some xfs kernel function spend much time (xfs_inobt_get_rec,
xfs_btree_increment, etc.)

I found a bug in bugzilla [1], is that is the same issue like this?

It's very greatly appreciated if you can give constructive suggestion about
this issue, as It's really hard to reproduce from another system and it's
not possible to do upgrade on that online machine.


[1] https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=813137

Thanks in advance
Qiang
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